RRB JE CBT-1 2024-25 18 December 2024 Shift 3 GK Questions – with answers & solutions

Answer: Option 3 — 2
Light can pass through a lens from either side, so a lens has two principal foci, F₁ and F₂, one on each side of the optical centre.
Revision note — Terms of a spherical lens
• Optical centre (O) — the central point of the lens; a ray through it goes undeviated.
• Principal focus — convex lens: parallel rays converge to it (real); concave lens: they appear to diverge from it (virtual).
• Focal length (f) — distance from the optical centre to a principal focus.
• Lens formula: 1/v − 1/u = 1/f; magnification m = v/u.
• Power P = 1/f (f in metres); unit dioptre (D); convex lens +, concave lens −.
• Convex lens: object between F and O ⇒ image virtual, erect, magnified (magnifying glass).
Do not mix these up
• Lens vs mirror — a lens has two principal foci; a spherical mirror has only one, because light never passes through a mirror.
Also asked from this topic: a ray through the optical centre (undeviated); lens that focuses parallel rays (convex); image of an object between O and F of a convex lens (virtual, erect, magnified).

Answer: Option 1 — Michael Faraday
In 1831 Michael Faraday showed that a changing magnetic field through a coil induces a current in it — electromagnetic induction.
Revision note — Electromagnetic induction
• Faraday's law — induced emf is proportional to the rate of change of magnetic flux.
• Lenz's law — the induced current flows so as to oppose the change that produced it.
• Induced current increases with more turns, a stronger magnet and faster motion.
• Fleming's right-hand rule gives the direction of induced current (generator); left-hand rule gives the force on a conductor (motor).
• Applications: AC generator (dynamo), transformer, induction cooktop, metal detector.
• Unit of capacitance, the farad (F), is named after Faraday.
Do not mix these up
• Oersted vs Faraday — Oersted (1820): electric current produces magnetism; Faraday (1831): changing magnetism produces current.
Also asked from this topic: direction of induced current (opposes the change in flux — Lenz's law); principle of generators (electromagnetic induction); a larger induced current (more turns, faster motion).

Answer: Option 4 — Spectrum
When white light splits into its colours (dispersion), the band of colours formed is called the spectrum — VIBGYOR.
Revision note — Dispersion of light
• Dispersion — splitting of white light into its component colours by a glass prism.
• Cause — each colour has a different wavelength, so it bends by a different amount in glass.
• Violet bends the most, red the least; red has the longest wavelength.
• Isaac Newton first obtained the spectrum of sunlight with a prism (1666).
• An inverted second prism recombines the colours into white light.
• A rainbow forms by refraction, dispersion and internal reflection in raindrops; it is seen with the Sun behind the observer.
Do not mix these up
• Dispersion vs spectrum — dispersion is the process; the spectrum is the band of colours it produces.
• Dispersion vs scattering — dispersion gives the rainbow; scattering gives the blue sky and red sunset.
Also asked from this topic: cause of spectrum formation by a prism (dispersion); who first explained dispersion (Isaac Newton); effect of an inverted second prism (recombines into white light).

Mirror formula.
1/v + 1/u = 1/f
Signs (New Cartesian convention).
Object is in front of the mirror ⇒ u = −30 cm
Focus of a convex mirror is behind it ⇒ f = +15 cm
Find v.
1/v = 1/f − 1/u
1/v = 1/15 − 1/(−30)
1/v = 1/15 + 1/30
1/v = 2/30 + 1/30 = 3/30 = 1/10
v = +10 cm
The + sign means the image is behind the mirror — virtual and erect.
Answer: 10 cm
Revision note — Mirror formula and sign convention
• Mirror formula: 1/v + 1/u = 1/f; for a spherical mirror f = R/2.
• Object distance u is always negative (object in front of the mirror).
• Concave mirror: f negative; convex mirror: f positive.
• Positive v ⇒ image behind the mirror (virtual); negative v ⇒ image in front (real).
• Magnification m = −v/u; here m = −10/(−30) = +1/3 — erect and diminished.
Also asked from this topic: a convex mirror of R = 2 m with a car 3 m away (image 0.75 m behind the mirror); where a parallel beam appears to diverge from a convex mirror of R = 50 cm (25 cm behind the mirror).
Option 2 (−10 cm) comes from taking f as −15 cm — a convex mirror's focal length is positive.

Energy used.
Energy (kWh) = power (kW) × time (hours)
Power = 400 W = 0.4 kW
Time = 8 h/day × 30 days = 240 h
Energy = 0.4 × 240 = 96 kWh
Cost.
Cost = energy × rate
Cost = 96 × ₹3 = ₹288
Answer: ₹288
Revision note — Electrical energy and its commercial unit
• 1 kWh = 1 kW used for 1 hour = 1 unit of electricity.
• 1 kWh = 3.6 × 10^(6) J.
• Electric power P = VI = I²R = V²/R; unit watt.
• Always change W to kW (÷ 1000) before multiplying by hours.
Also asked from this topic: the units used by a 60 W lamp for 5 hours a day for 30 days (9 units); the cost of running a 2.2 kW kettle for 30 minutes at ₹4 per unit (₹4.40).
₹36 comes from forgetting the 8 hours a day — count total hours before multiplying.

Answer: Option 3 — anti-clockwise
Look at the face of the loop from the front.
If the current flows anti-clockwise, that face behaves as a North pole; if clockwise, it is a South pole.
Revision note — Magnetic field of a current-carrying loop
• Clock-face rule: anti-clockwise current ⇒ North pole; clockwise current ⇒ South pole (as seen by the viewer).
• Right-hand thumb rule: curl the fingers along the current, the thumb points along the magnetic field inside the loop.
• At the centre of the loop the field lines are almost straight and perpendicular to the plane of the loop.
• Field at the centre increases with the current and the number of turns, and decreases as the radius increases.
• A solenoid (many turns) behaves like a bar magnet; with a soft iron core it becomes an electromagnet.
Do not mix these up
• Direction of current vs direction of field — the pole depends on how the current circulates, not on "north" or "south" as a direction of flow.
Also asked from this topic: the rule used for the field at the centre of a circular loop (right-hand thumb rule).

Answer: Option 4 — the direction of force on a current-carrying conductor
Fleming's left-hand rule tells the direction of the force (motion) on a conductor carrying current in a magnetic field.
It gives direction only — the magnitude comes from F = BIL.
Revision note — Fleming's left-hand rule
• Stretch the thumb, forefinger and middle finger of the left hand mutually perpendicular.
• Forefinger → magnetic field; middle finger → current; thumb → force / motion.
• Force is maximum when the current is perpendicular to the field and zero when parallel.
• Reversing either the current or the field reverses the force.
• Devices based on it: electric motor, loudspeaker, galvanometer.
Do not mix these up
• Left-hand vs right-hand rule — left for motor (force on a current); right for generator (direction of induced current).
Also asked from this topic: which finger shows the magnetic field (forefinger); what happens to the force if the current is reversed (it reverses).

Answer: Option 2 — heating effect of the current flowing through the fan
The current in the fan's copper windings meets resistance.
Part of the electrical energy turns into heat (Joule heating), so the fan warms up over time.
Revision note — Heating effect of electric current
• Joule's law: H = I^(2)Rt — heat ∝ square of current, resistance and time.
• Doubling the current makes the heat four times.
• Useful applications: electric iron, heater, toaster, geyser, bulb filament, fuse.
• Heater coils use nichrome — high resistivity and high melting point.
• Bulb filament: tungsten (melting point about 3380 °C); bulbs are filled with nitrogen / argon.
• In motors, fans and transformers this heat is wasted energy.
Also asked from this topic: the change in heat when current is doubled (four times); why nichrome is used in heaters (high resistivity and high melting point).

Answer: Option 4 — Virtual, erect and point sized
Parallel rays from an object at infinity diverge after passing through a concave lens.
They appear to come from the focus F_(1).
So the image is virtual, erect and highly diminished (point-sized), on the same side as the object.
Revision note — Image formation by a concave lens
• Object at infinity → image at F_(1); virtual, erect, highly diminished (point-sized).
• Object anywhere between infinity and the lens → image between F_(1) and the optical centre; virtual, erect, diminished.
• A concave lens always gives a virtual, erect, diminished image — it can never give a real image of a real object.
• Sign convention: focal length and power of a concave lens are negative.
• Uses: correcting myopia, peepholes in doors, the upper part of bifocal lenses.
Do not mix these up
• Concave lens vs convex lens (object at infinity) — convex gives a real, inverted, point-sized image at F_(2) on the other side; concave gives a virtual, erect one at F_(1) on the same side.
Also asked from this topic: image size by a concave lens for any object (always diminished); a lens of power −2.5 D (concave); the lens used to correct myopia (concave).

Answer: Option 1 — Fuse
A fuse is a wire of low melting point placed in series with the circuit.
When the current becomes too large, the wire heats up and melts, breaking the circuit and saving the appliances.
Revision note — Electric fuse and household safety
• A fuse works on the heating effect of current (Joule's law, H = I²Rt).
• Fuse wire is an alloy (e.g. tin–lead) with low melting point and suitable resistance; it sits in a porcelain cartridge.
• It is always put in the live wire, in series with the appliance.
• Indian homes use a 5 A circuit for lights and fans and a 15 A circuit for geysers, ACs and heaters.
• Overloading (too many appliances on one socket) and short-circuit (live touching neutral) both cause excess current.
• Wire colours: live — red/brown, neutral — black/blue, earth — green; modern homes use an MCB in place of a fuse.
Do not mix these up
• Fuse vs earthing — a fuse guards against excess current; earthing guards the user against shock from a leaking metal body.
Also asked from this topic: the main use of a fuse in a household circuit (to break the circuit when excess current flows); the current rating for heavy appliances (15 A).

Answer: Option 1 — Appointment of Supreme Court judges
Judges of the Supreme Court are appointed by the President under Article 124(2), on the recommendation of the collegium headed by the Chief Justice of India — the Prime Minister has no such function.
Revision note — Prime Minister of India
• The PM is appointed by the President under Article 75(1); other ministers are appointed by the President on the PM's advice.
• Article 74 — a Council of Ministers headed by the PM aids and advises the President.
• The PM allocates portfolios and can ask a minister to resign or advise the President to dismiss him.
• Article 78 — the PM must communicate Cabinet decisions to the President.
• The PM can advise the President to dissolve the Lok Sabha; the Rajya Sabha is a permanent house and is never dissolved.
• The PM is ex-officio chairman of NITI Aayog and the Inter-State Council.
Do not mix these up
• Appointment of ministers vs appointment of judges — ministers: President on the PM's advice; Supreme Court judges: President on the collegium's recommendation.
Also asked from this topic: who appoints the Prime Minister (the President); the head of the Union Council of Ministers (the Prime Minister); the chairman of the Inter-State Council (the Prime Minister).

Answer: Option 1 — 14
Article 24 bars the employment of any child below 14 years in a factory, mine or any other hazardous employment.
Revision note — Right against Exploitation and child rights
• Articles 23–24 form the Right against Exploitation (Part III, Fundamental Rights).
• Article 23 — bans traffic in human beings, begar and other forced labour.
• Article 21A — free and compulsory education for children aged 6–14 (86th Amendment, 2002).
• Article 45 (DPSP) — early childhood care and education for children below 6.
• Article 51A(k) — duty of parents to provide education to children aged 6–14.
• Child Labour Amendment Act, 2016 — no child below 14 in any work; adolescents 14–18 barred from hazardous work.
Also asked from this topic: Article against trafficking and forced labour (Article 23); Articles forming the Right against Exploitation (23–24); Article on child labour below 14 (Article 24).

Answer: Option 2 — Article 368
Article 239A lets Parliament create, by an ordinary law, a legislature and/or a Council of Ministers for Puducherry.
Clause (2) says such a law is not an amendment of the Constitution for the purposes of Article 368, even if it changes constitutional provisions.
So it needs only a simple majority, not the special majority of Article 368.
Revision note — Union Territories (Part VIII, Articles 239–242)
• Article 239: every UT is administered by the President through an administrator he appoints.
• Article 239A: legislature / council of ministers for Puducherry — inserted by the 14th Amendment, 1962.
• Article 239AA: special provisions for Delhi (NCT) — inserted by the 69th Amendment, 1991.
• Article 240: President's power to make regulations for certain UTs (Andaman & Nicobar, Lakshadweep, etc.).
• Article 368: procedure to amend the Constitution (Part XX).
• UTs with legislatures today: Delhi, Puducherry, Jammu and Kashmir.
Do not mix these up
• Article 239A vs 239AA — 239A → Puducherry; 239AA → Delhi.
Also asked from this topic: who appoints the administrator of a Union Territory (the President); the UT that has a Vidhan Sabha among Puducherry, Chandigarh, Lakshadweep and Andaman (Puducherry).

Answer: Option 1 — Strawberry
A runner is a thin stem that creeps along the soil surface; at its nodes it strikes roots and a new plant grows — the strawberry spreads this way.
Revision note — Vegetative propagation
• New plants grow from root, stem or leaf of one parent — asexual, so offspring are genetically identical (clones).
• Runners / stolons — strawberry, doob grass, Oxalis.
• Stem tuber — potato (new plants from the eyes); rhizome — ginger, turmeric; bulb — onion.
• Root tuber — sweet potato, dahlia; leaf buds — Bryophyllum.
• Artificial methods — cutting (rose, sugarcane), layering (jasmine), grafting (mango), tissue culture (orchids).
• Useful for plants that give no viable seeds (banana, orange, rose) and to keep good traits of the parent.
Also asked from this topic: the key feature of vegetative propagation (new plants from roots, stems or leaves, not seeds); why farmers prefer cutting, grafting and tissue culture (they give genetically identical plants).

Answer: Option 3 — Egg cell
The ovule inside the ovary holds the embryo sac, and the egg cell in it is the female germ cell (gamete) that fuses with the male gamete.
Revision note — Sexual reproduction in flowering plants
• Stamen (anther + filament) is the male part; pistil / carpel (stigma, style, ovary) is the female part.
• Anther makes pollen grains, which carry the male gametes.
• Ovary contains ovules; each ovule has an egg cell.
• Pollination — transfer of pollen from anther to stigma; the pollen tube grows through the style to the ovule.
• Fertilisation — male gamete + egg cell ⇒ zygote ⇒ embryo.
• After fertilisation: ovule ⇒ seed, ovary ⇒ fruit; petals, sepals and stamens wither.
Do not mix these up
• Pollination vs fertilisation — pollination is transfer of pollen; fertilisation is fusion of gametes.
Also asked from this topic: pollination : transfer of pollen :: fertilisation : (fusion of gametes); the name for reproductive cells made by meiosis (gametes); pollen tube growing towards the ovule (chemotropism).

Answer: Option 1 — Gonorrhoea
Gonorrhoea is caused by the bacterium Neisseria gonorrhoeae and spreads through sexual contact, so it is a bacterial STD.
Revision note — Sexually transmitted diseases (STDs)
• Bacterial STDs — gonorrhoea (Neisseria gonorrhoeae), syphilis (Treponema pallidum), chlamydia; treated with antibiotics.
• Viral STDs — HIV-AIDS, genital warts (HPV), genital herpes, hepatitis B; antibiotics do not work on them.
• Condoms (barrier method) reduce STD spread; surgical methods (vasectomy, tubectomy) prevent pregnancy but not infection.
• Other bacterial diseases spread differently — tuberculosis through air (BCG vaccine), typhoid through contaminated food and water (Widal test).
• Pneumonia is usually bacterial (Streptococcus pneumoniae) and spreads through droplets.
Also asked from this topic: a limitation of surgical contraception (it does not prevent sexually transmitted infections); the test that confirms typhoid (Widal test); the first antibiotic (penicillin).

Answer: Option 2 — 44+XX
The egg always carries 22 + X; an X-bearing sperm also carries 22 + X.
Together they give 44 autosomes + XX — the child is a girl.
Revision note — Sex determination in humans (Class 10)
• Humans have 46 chromosomes = 23 pairs: 22 pairs of autosomes + 1 pair of sex chromosomes.
• Female: 44 + XX; male: 44 + XY.
• Every egg carries 22 + X; a sperm carries either 22 + X or 22 + Y.
• The father's sperm decides the sex of the child — X-sperm ⇒ girl, Y-sperm ⇒ boy.
• Each fertilisation has a 50% chance of either sex.
• In some reptiles sex is decided by incubation temperature of the eggs, not by chromosomes.
Do not mix these up
• 46 vs 44 — 46 is the total count; 44 is the autosome count written before XX / XY.
Also asked from this topic: the number of pairs of autosomes in humans (22); the number of chromosomes in a normal human zygote (46).
46+XX would mean 48 chromosomes in all — the autosome count is 44.

Answer: Option 2 — the nutrients in the mother's blood nourishes the growing baby
The embryo gets its food from the mother's blood through the placenta.
So whatever the mother eats decides the nutrients reaching the baby — salads and fruits give vitamins, minerals and fibre.
Revision note — Nourishment of the embryo (Class 10)
• The zygote divides to form an embryo, which gets implanted in the wall of the uterus.
• The placenta is a disc-like tissue embedded in the uterine wall that links mother and embryo.
• Villi on the embryo's side of the placenta give a large surface area for exchange.
• Glucose and oxygen pass from the mother's blood to the embryo; wastes pass back to the mother's blood.
• The time from fertilisation to birth in humans is about nine months.
• A pregnant woman needs extra protein, iron, calcium, folic acid and vitamins.
Also asked from this topic: the immunity a foetus gets from antibodies crossing the placenta (passive natural immunity).
Option 3 states the opposite of the truth — the mother's blood is the baby's only supply line.

Answer: Option 2 — They are not always a perfect pair in males.
Women have a matched pair of sex chromosomes, XX.
Men have a mismatched pair, XY — the Y is much shorter than the X.
Revision note — Sex determination in humans
• Humans have 46 chromosomes in 23 pairs: 22 pairs of autosomes + 1 pair of sex chromosomes.
• Female: XX — all eggs carry X.
• Male: XY — half the sperms carry X, half carry Y.
• The father's sperm decides the sex of the child: X sperm ⇒ girl, Y sperm ⇒ boy.
• Chance of a boy or a girl in each birth = 50%.
• In some reptiles (turtles, crocodiles) sex is decided by the temperature at which eggs are kept.
Do not mix these up
• Autosomes vs sex chromosomes — autosomes are always in matched pairs in both sexes; only the sex-chromosome pair differs in males.
Also asked from this topic: the number of pairs of autosomes in humans (22).

Answer: Option 3 — It is a form of sexual reproduction.
Fragmentation is asexual — one parent simply breaks into pieces and each piece grows into a new individual.
No gametes are formed and no fertilisation takes place.
Revision note — Modes of asexual reproduction
• Fragmentation: body breaks into pieces, each grows into a new organism — Spirogyra, many filamentous algae.
• Regeneration: a cut piece rebuilds the whole body using specialised cells — Planaria, Hydra.
• Fission: binary in Amoeba, Paramecium; multiple in Plasmodium (malaria parasite).
• Budding: a bud grows out and detaches — Hydra, yeast.
• Spore formation: Rhizopus (bread mould) — spores in sporangia.
• Vegetative propagation: new plants from roots, stems, leaves — Bryophyllum (leaf), potato (stem tuber).
Do not mix these up
• Fragmentation vs regeneration — fragmentation is a normal way of reproducing; regeneration is rebuilding after an injury and is not the usual reproduction method.
Also asked from this topic: what single-parent reproduction in Amoeba, yeast and Hydra shows (it occurs without fusion of gametes).

Answer: Option 4 — vegetative propagation is by buds (eyes)
A potato is a stem tuber; its eyes are buds that sprout into new shoots.
Growing a new plant from such a part without seeds is vegetative propagation.
Revision note — Vegetative propagation
• An asexual method: new plants grow from root, stem or leaf of one parent — no seeds, no gametes.
• Stem tuber: potato (eyes = buds); rhizome: ginger, turmeric; bulb: onion; runner: grass, strawberry.
• Leaf buds: Bryophyllum forms buds on the leaf margin that fall and grow into plants.
• Artificial methods: cutting (rose, sugarcane), layering (jasmine), grafting (mango), tissue culture (orchids, banana).
• Advantages: plants are genetically identical to the parent, bear flowers and fruits earlier, and seedless plants (banana, orange, grape, rose) can be grown.
Do not mix these up
• Potato vs sweet potato — potato is a modified stem (it has eyes/buds); sweet potato is a modified root.
Also asked from this topic: why farmers use cutting and grafting (identical plants); the wrong statement about vegetative propagation ("new plants develop from seed-bearing structures").

Answer: Option 4 — Population control
Family planning helps couples decide the number and spacing of children by using contraceptive methods.
Its main national aim is to check population growth.
Revision note — Reproductive health and contraception
• Barrier methods: condom, diaphragm — stop sperm reaching the egg; condoms also protect against STDs.
• Hormonal methods: oral pills change the hormonal balance so eggs are not released.
• IUCDs: Copper-T or loop placed in the uterus to prevent pregnancy.
• Surgical methods: vasectomy (vas deferens blocked in males) and tubectomy (fallopian tubes blocked in females).
• Female foeticide after prenatal sex determination is illegal in India.
• India launched the world's first government National Family Planning Programme in 1952.
Do not mix these up
• Family planning vs abortion — family planning prevents unwanted pregnancy by contraception; it does not recommend abortion.
Also asked from this topic: the year India introduced its Family Planning Programme (1952); the number of high-focus states first covered by Mission Parivar Vikas (7).

Answer: Option 3 — Stem cutting is a type of asexual reproduction, so there was no variation.
A stem cutting grows from one parent without any fusion of gametes.
Its DNA is a copy of the parent's, so the new plant bears the same white flowers.
Revision note — Asexual reproduction and variation
• Asexual reproduction: one parent, no gametes; offspring are clones of the parent.
• Only tiny variations arise, from small errors in DNA copying.
• Sexual reproduction combines DNA from two parents, so it produces more variation.
• Variation helps a species survive changes in its surroundings.
• Stem cutting is used for rose, sugarcane, money plant; grafting for mango; layering for jasmine.
• Gardeners use cutting and grafting to keep a desired trait (flower colour, fruit quality) unchanged.
Do not mix these up
• Cutting vs grafting — a cutting grows on its own roots; in grafting a scion is joined to the stock of another plant.
Also asked from this topic: why farmers prefer cutting and grafting (identical plants); the wrong statement about vegetative propagation ("new plants develop from seed-bearing structures").

Answer: Option 4 — Astana, Kazakhstan
The 19th meeting of the Secretaries of the Security Councils of SCO member states was held at Astana in April 2024, because Kazakhstan held the SCO chair for 2023–24.
Revision note — Shanghai Cooperation Organisation (SCO)
• Founded 15 June 2001 at Shanghai by China, Russia, Kazakhstan, Kyrgyzstan, Tajikistan, Uzbekistan (from the Shanghai Five, 1996).
• India and Pakistan became full members in 2017 (Astana summit); Iran joined in 2023, Belarus in July 2024.
• Secretariat — Beijing; RATS (Regional Anti-Terrorist Structure) — Tashkent.
• Official languages — Russian and Chinese.
• The 18th Security Council Secretaries' meeting was held at New Delhi in 2023, during India's chairship.
• The 2024 Heads of State summit was also held at Astana (July 2024).
Also asked from this topic: the year SCO was established (2001); the year India became a full member (2017); the body RATS belongs to (SCO); the official languages of SCO (Russian and Chinese).

Answer: Option 1 — Thailand
Chiang Mai is a city in northern Thailand; in March 2024 it topped IQAir's live list of the world's most polluted cities because of haze from forest fires and crop-residue burning in the dry season.
Revision note — Air-pollution rankings (as at 2024)
• IQAir is a Swiss air-quality technology company; its rankings are based on PM2.5 levels.
• PM2.5 — particles smaller than 2.5 micrometres; they reach deep into the lungs.
• World Air Quality Report 2023 (released March 2024): most polluted country Bangladesh, then Pakistan, then India (3rd).
• The same report named Begusarai (Bihar) the most polluted metropolitan area and New Delhi the most polluted capital.
• WHO annual guideline for PM2.5 — 5 µg/m³ (2021).
• As of 2026: in the 2024 report (March 2025) Byrnihat (Meghalaya) was the most polluted city and India ranked 5th.
Also asked from this topic: the most polluted capital city in the World Air Quality Report 2023 (New Delhi); the most polluted place in the 2024 report (Byrnihat, Meghalaya); India's rank in the 2024 report (5th).

Answer: Option 3 — Rajiv Ranjan Singh
In the third Modi ministry sworn in on 9 June 2024, Rajiv Ranjan Singh (Lalan Singh) of JD(U) became Union Minister of Panchayati Raj.
He also holds Fisheries, Animal Husbandry and Dairying.
Revision note — Portfolios in the Union Cabinet, June 2024
• J. P. Nadda: Health and Family Welfare; Chemicals and Fertilizers.
• Shivraj Singh Chouhan: Agriculture and Farmers' Welfare; Rural Development.
• Piyush Goyal: Commerce and Industry.
• Ministry of Panchayati Raj was created in May 2004; the 73rd Amendment (1992) gave panchayats constitutional status.
• National Panchayati Raj Day: 24 April.
• Flagship MoPR scheme: SVAMITVA (property cards for rural houses using drones).
Do not mix these up
• Panchayati Raj vs Rural Development — two separate ministries; Rural Development went to Shivraj Singh Chouhan.
Also asked from this topic: the ministry that runs the SVAMITVA scheme (Ministry of Panchayati Raj).

Answer: Option 2 — Siddhartha Agarwal
Bengaluru swimmer Siddhartha Agarwal, aged 49, swam solo across the English Channel on 29 August 2024.
He took about 15 hours 6 minutes, becoming the oldest Indian to do so.
Revision note — English Channel and Indian swimmers
• The English Channel separates England from France; the narrowest point is the Strait of Dover.
• Mihir Sen (1958) was the first Indian to swim the English Channel.
• Arati Saha (1959) was the first Asian woman to swim it.
• In July 2024, para swimmer Jiya Rai became the youngest and fastest female para swimmer to cross it solo.
• Srihari Nataraj (backstroke) and Virdhawal Khade (freestyle) are India's leading pool swimmers; open-water records are a separate category.
Also asked from this topic: the para swimmer who became the youngest and fastest female para swimmer to cross the English Channel in July 2024 (Jiya Rai).

Answer: Option 2 — EOS-08
ISRO marked its 55th foundation day (founded 15 August 1969) with the launch of the Earth Observation Satellite EOS-08 on SSLV-D3 from Sriharikota.
The launch took place on 16 August 2024, a day after the anniversary itself.
Revision note — EOS-08 and SSLV-D3
• SSLV-D3 was the third and final developmental flight of the Small Satellite Launch Vehicle.
• EOS-08 (about 175 kg) was placed in a 475 km circular low Earth orbit; planned life 1 year.
• Payloads: EOIR (electro-optical infrared imaging), GNSS-R (reflectometry for soil moisture, ocean winds, floods) and a SiC UV dosimeter for Gaganyaan.
• SSLV: three solid stages plus a liquid Velocity Trimming Module; carries up to 500 kg to low Earth orbit; built for low-cost, on-demand launches.
• Earlier EOS: EOS-07 on SSLV-D2 (Feb 2023); EOS-06 (Oceansat-3) on PSLV-C54 (Nov 2022); EOS-04 (RISAT-1A) on PSLV-C52 (Feb 2022).
• ISRO was founded under Vikram Sarabhai; headquarters Bengaluru.
Also asked from this topic: what sets the SSLV apart (low-cost, on-demand launches); the lift-off mass of the SSLV (about 120 tonnes); the satellite SSLV-D2 placed in orbit (EOS-07).

Answer: Option 4 — calcium sulphate hemihydrate
Plaster of Paris is CaSO_(4)·½H_(2)O — two formula units of calcium sulphate share one water molecule.
"Hemi" means half.
Revision note — Plaster of Paris and gypsum (Class 10)
• Gypsum = CaSO_(4)·2H_(2)O (calcium sulphate dihydrate).
• Heating gypsum at 373 K gives Plaster of Paris: CaSO_(4)·2H_(2)O → CaSO_(4)·½H_(2)O + 1½H_(2)O.
• Mixed with water, Plaster of Paris sets into a hard solid mass — it changes back to gypsum.
• Uses: plaster for supporting fractured bones, toys, decoration material, making surfaces smooth.
• It is stored in moisture-proof containers, since moisture makes it set.
Do not mix these up
• Hemihydrate vs dihydrate — Plaster of Paris is ½H_(2)O; gypsum is 2H_(2)O.
Also asked from this topic: the process by which Plaster of Paris hardens with water (rehydration to form gypsum); why it is used for casts on fractured bones (sets quickly into a hard mass).
Option 1 (dihydrate) is gypsum, the raw material — not Plaster of Paris.

Answer: Option 3 — double displacement reaction
In neutralisation the acid and the base exchange ions: NaOH + HCl → NaCl + H_(2)O.
Na⁺ pairs with Cl⁻ and H⁺ pairs with OH⁻ — an exchange of partners is a double displacement.
Revision note — Neutralisation (Class 10)
• Acid + base → salt + water; the reaction is exothermic (gives out heat).
• The core step is H⁺ + OH⁻ → H_(2)O.
• Double displacement: two compounds exchange ions (AB + CD → AD + CB).
• A double displacement that forms an insoluble solid is a precipitation reaction (BaCl_(2) + Na_(2)SO_(4) → BaSO_(4)↓ + 2NaCl).
• Everyday uses: antacids (milk of magnesia) for acidity, baking soda on bee stings, quicklime / slaked lime for acidic soil.
Do not mix these up
• Displacement vs double displacement — displacement: one element pushes another out (Zn + CuSO_(4)); double displacement: two compounds swap ions.
Also asked from this topic: the products when an acid reacts with a base (salt and water); what is added to acidic soil to neutralise it (quicklime).
Neutralisation forms two new compounds from two compounds — no single element is displaced.

Answer: Option 3 — loses water molecules and becomes powdery
Washing soda is Na_(2)CO_(3)·10H_(2)O.
In warm, dry air it loses 9 of its 10 water molecules and crumbles into a white powder (Na_(2)CO_(3)·H_(2)O).
This loss of water on exposure to air is called efflorescence.
Revision note — Water of crystallisation (Class 10)
• Water of crystallisation = the fixed number of water molecules in one formula unit of a salt crystal.
• Washing soda Na_(2)CO_(3)·10H_(2)O (10 H_(2)O); blue vitriol CuSO_(4)·5H_(2)O (5); gypsum CaSO_(4)·2H_(2)O (2); Plaster of Paris CaSO_(4)·½H_(2)O.
• Heating blue copper sulphate crystals drives off water — they turn white (anhydrous); adding water brings the blue back.
• The shape and colour of crystals depend on this water; losing it breaks the crystal.
• Washing soda is made by recrystallising sodium carbonate (from the Solvay process); uses: glass, soap, paper, removing permanent hardness of water.
Do not mix these up
• Efflorescence vs deliquescence — efflorescence: a salt loses water to air (washing soda); deliquescence: a salt absorbs water from air and dissolves (CaCl_(2), NaOH).
Also asked from this topic: the industries that use washing soda (glass, soap and paper).
A crystal cannot keep its crystal form after losing its water of crystallisation — option 4 is the trap.

Answer: Option 4 — barium sulphate
The ions exchange partners: Ba²⁺ joins SO₄²⁻ and Na⁺ joins Cl⁻.
Barium sulphate is insoluble, so it separates as a white precipitate; sodium chloride stays dissolved.
Revision note — Double displacement and precipitation reactions
• Double displacement: two compounds exchange ions (AB + CD → AD + CB).
• A reaction that gives an insoluble solid (precipitate) is a precipitation reaction.
• BaSO_(4) — white precipitate; PbI_(2) — yellow precipitate (lead nitrate + potassium iodide).
• Neutralisation (acid + base → salt + water) is also a double displacement reaction.
• In this reaction no oxidation or reduction takes place — oxidation states stay the same.
Do not mix these up
• Displacement vs double displacement — displacement: a metal pushes out another metal (Fe + CuSO_(4)); double displacement: two compounds swap ions.
Also asked from this topic: the state symbol of BaSO_(4) in this reaction ((s)); the type of reaction shown by the white precipitate (double displacement / precipitation).

Answer: Option 3 — Ca(OH)_(2) + Cl_(2)
Bleaching powder is made by passing chlorine gas (Cl_(2)) over dry slaked lime, Ca(OH)_(2).
Ca(OH)_(2) + Cl_(2) → CaOCl_(2) + H_(2)O
Revision note — Bleaching powder
• Chemical name calcium oxychloride, formula CaOCl_(2).
• Chlorine comes from the chlor-alkali process (electrolysis of brine).
• Brine gives NaOH, Cl_(2) at the anode and H_(2) at the cathode.
• Its action comes from the chlorine it releases.
• Uses: bleaching cotton, linen and wood pulp; disinfecting drinking water; oxidising agent in industry.
• Other salts: baking soda NaHCO_(3), washing soda Na_(2)CO_(3)·10H_(2)O, Plaster of Paris CaSO_(4)·½H_(2)O.
Do not mix these up
• Slaked lime vs quicklime — slaked lime is Ca(OH)_(2); quicklime is CaO. Bleaching powder needs slaked lime.
Also asked from this topic: the gas that gives bleaching powder its action (chlorine); another use of bleaching powder (disinfecting water); the process that gives chlorine from brine (chlor-alkali process).

Answer: Option 4 — Quick lime dissolved in water
Quick lime combines with water to form one product, slaked lime, and gives out a lot of heat:
CaO + H_(2)O → Ca(OH)_(2) + heat
So it is both a combination and an exothermic reaction.
Revision note — Combination and exothermic reactions
• Combination reaction: two or more reactants form a single product (A + B → AB).
• Quick lime = calcium oxide (CaO); slaked lime = calcium hydroxide (Ca(OH)_(2)), used for whitewashing.
• Whitewash turns shiny in 2–3 days as Ca(OH)_(2) reacts with CO_(2) to form calcium carbonate (CaCO_(3)).
• Other exothermic combinations: burning of coal (C + O_(2) → CO_(2)); 2H_(2) + O_(2) → 2H_(2)O.
• Exothermic = heat released; endothermic = heat absorbed (e.g. photosynthesis, most decomposition reactions).
• Dissolving ammonium chloride in water absorbs heat — the solution turns cold.
Do not mix these up
• Respiration — it is exothermic, but glucose breaks down into CO_(2) and water, so it is not a combination reaction.
Also asked from this topic: the type of reaction CaO + H_(2)O → Ca(OH)_(2) (combination); an example of an exothermic reaction (combustion of petrol).

Answer: Option 4 — reduces to form brownish copper metal
Hot copper(II) oxide loses oxygen to hydrogen, so it is reduced to reddish-brown copper:
CuO (black) + H_(2) → Cu (brown) + H_(2)O
At the same time hydrogen gains oxygen and is oxidised to water.
Revision note — Oxidation and reduction
• Oxidation: gain of oxygen or loss of hydrogen; reduction: loss of oxygen or gain of hydrogen.
• Both happen together — a redox reaction.
• Here CuO is the oxidising agent and H_(2) the reducing agent.
• Reverse change: heating copper in air, 2Cu + O_(2) → 2CuO — brown surface turns black.
• Another example: ZnO + C → Zn + CO (ZnO reduced, carbon oxidised).
• Blue colour belongs to copper sulphate solution, not to copper metal.
Do not mix these up
• What is reduced vs what is oxidised — CuO is reduced (to Cu); hydrogen is oxidised (to H_(2)O).
Also asked from this topic: what is oxidised and what is reduced in CuO + H_(2) → Cu + H_(2)O (hydrogen oxidised, CuO reduced).

Answer: Option 2 — Bengal
The Indigo Revolt (Neel Vidroha) of 1859–60 broke out in Bengal, starting in the Nadia district.
Ryots refused to grow indigo for European planters who forced it on them through advances and violence.
Revision note — Indigo Revolt, 1859–60
• Leaders: Digambar Biswas and Bishnu Biswas of Govindpur village, Nadia.
• Planters forced ryots to sign contracts (dadni advances) and grow indigo on their best land.
• The play Neel Darpan (Dinabandhu Mitra, 1860) showed the planters' cruelty; its English translation led to the trial of Rev. James Long.
• Harish Chandra Mukherjee backed the ryots in his paper Hindu Patriot.
• The government set up the Indigo Commission (1860), which ruled that ryots could not be forced to grow indigo.
• The planters then shifted to Bihar (Champaran), where Gandhi's Champaran Satyagraha (1917) later took place.
Also asked from this topic: where the indigo planters moved after the revolt in Bengal (Bihar); the year of Gandhi's Champaran movement (1917).

Answer: Option 2 — 2021
Reflections on Mughal Art and Culture, an illustrated collection of essays edited by art historian Roda Ahluwalia, was published by Niyogi Books in 2021.
Revision note — Mughal art and painting
• Mughal painting began under Humayun, who brought Persian masters Mir Sayyid Ali and Abdus Samad.
• Akbar set up a large royal atelier; the Hamzanama was its first big project; Daswant and Basawan were leading painters.
• Painting reached its peak under Jahangir — Ustad Mansur (birds and animals) and Abu'l Hasan were his masters.
• Shah Jahan's reign is the high point of Mughal architecture — Taj Mahal, Red Fort (Delhi), Jama Masjid.
• Aurangzeb withdrew patronage, and painters moved to Rajput and Pahari courts.
Also asked from this topic: the Mughal emperor who claimed he could identify the painter of any picture (Jahangir).

Answer: Option 4 — Ajanta Caves
The Ajanta Caves in Maharashtra are rock-cut Buddhist caves famous for their murals (paintings) and sculptures.
They were inscribed as a UNESCO World Heritage Site in 1983.
Revision note — Rock-cut cave sites and UNESCO
• Ajanta: about 30 Buddhist caves in Chhatrapati Sambhajinagar (Aurangabad) district, 2nd century BCE – 6th century CE.
• Many Ajanta caves were made under Vakataka patronage; murals show Jataka tales and the Padmapani Bodhisattva.
• Ellora: 34 caves of Buddhist, Hindu and Jain faiths; the monolithic Kailasa temple (Cave 16) was built by the Rashtrakuta Krishna I; UNESCO 1983.
• Elephanta: on Gharapuri island near Mumbai; Shaivite sculptures, the Trimurti (Maheshmurti); UNESCO 1987.
• Bhimbetka: prehistoric rock shelters and paintings in Madhya Pradesh; UNESCO 2003.
• Badami: Chalukya rock-cut temples in Karnataka — not a UNESCO site (nearby Pattadakal is).
• India's first UNESCO sites (1983): Ajanta, Ellora, Agra Fort, Taj Mahal.
Do not mix these up
• Ajanta vs Ellora — Ajanta is only Buddhist and known for paintings; Ellora mixes three faiths and is known for the Kailasa temple.
• Ajanta vs Elephanta — both in Maharashtra, but Elephanta is known for sculpture, not paintings.
Also asked from this topic: the site whose paintings and sculptures are masterpieces of Buddhist art (Ajanta Caves); what makes the Elephanta Caves distinct (Shaivite themes and sculpture).

Answer: Option 4 — Relatively elastic
Under monopolistic competition each firm sells a differentiated product that has close substitutes.
If it raises its price, many buyers shift to rivals.
So its demand curve slopes downward and is relatively elastic (flatter than a monopolist's).
Revision note — Market structures and the firm's demand curve
• Perfect competition: very many sellers, homogeneous product, firm is a price taker — demand curve perfectly elastic (horizontal).
• Monopolistic competition: many sellers, product differentiation, selling costs (advertising), free entry — demand relatively elastic.
• Monopoly: single seller, no close substitute, strong entry barriers — demand less elastic, firm is a price maker.
• Oligopoly: few large, interdependent firms; demand curve is indeterminate (kinked-demand model).
• In the long run, free entry leaves monopolistic-competition firms with only normal profit.
• Monopolistic competition was developed by E.H. Chamberlin (1933); examples: soaps, toothpaste, restaurants.
Do not mix these up
• Perfectly elastic vs relatively elastic — perfectly elastic (horizontal) is the perfectly competitive firm; the monopolistic competitor has a sloping but elastic curve.
Also asked from this topic: short-run result under monopolistic competition (profit or loss); a feature that is NOT of oligopoly (infinite sellers); a feature of a perfectly competitive market (free entry and exit).

Answer: Option 3 — Dachigam
The Hangul (Kashmir stag) survives mainly in Dachigam National Park, near Srinagar, Jammu and Kashmir.
It is the only surviving red-deer subspecies in India and is protected under Project Hangul.
Revision note — Dachigam and the Hangul
• Hangul is the state animal of Jammu and Kashmir; IUCN status Critically Endangered.
• Dachigam was declared a national park in 1981; its name refers to the ten villages moved to create it.
• Project Hangul began in the 1970s with the J&K government, IUCN and WWF.
• Other animals of Dachigam: Himalayan black bear, leopard, musk deer.
• Dudhwa (UP) — swamp deer (barasingha) and rhino; Chandoli (Maharashtra) — part of Sahyadri Tiger Reserve.
• Campbell Bay — national park on Great Nicobar Island, part of the Great Nicobar Biosphere Reserve.
Do not mix these up
• Hangul vs sangai — Hangul is the Kashmir stag (Dachigam); sangai is the brow-antlered deer of Keibul Lamjao (Manipur).
Also asked from this topic: the animal targeted by Project Hangul (Kashmir stag).