Defence, nuclear & energy technology

Answer: (c) 1 and 2 only

Stealth technology aims to make an aircraft or ship nearly invisible to radar by shaping it and coating it with materials that absorb radar, so it sends back a very small echo. Coatings are meant to cut the returned signal, not to increase scattering.

• ✓ 1. Stealth designs aim for a very small radar cross-section, and radar-absorbing materials are a standard part of it. The B-2's stealth features include radar-absorbing materials, and its radar cross-section is reported to be like that of a small bird.
• ✓ 2. UPSC's official key treats this statement as correct; we could not confirm the detail from an official source, so we do not explain it here.
• ✗ 3. Britannica notes that surface materials and coatings are used to absorb radar transmissions and reduce reflections to the enemy's radar receiver. Increasing scattering would make the object easier to detect, which defeats the purpose.

Remember · Stealth = very small radar cross-section using shaping and radar-absorbing coatings; coatings reduce, never increase, the radar echo.

Question and answer: UPSC's provisional GS Paper I (2026, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 1 Oct 2026 (how we verify). Permalink · Report an error

Answer: (b) 2 and 3 only

A drone swarm is a large group of small unmanned systems that work together on a mission, and GPS spoofing is one of the recognised counter-UAS techniques.

• ✗ 1. UPSC's official key treats this statement as incorrect; we could not confirm the detail from an official source, so we do not explain it here.
• ✓ 2. A swarm is a group of drones that act together on one mission (PIB, DARPA). UPSC's official key treats the statement as correct; we could not confirm the rest of the detail from an official source, so we do not explain it here.
• ✓ 3. The NATO Science and Technology Organization lists GPS spoofing, with RF jamming, high-power lasers, EMP and projectile guns, among counter-UAS measures against small UAVs.

Remember · Swarm = many drones acting together on a mission. Counter-drone tools: RF jamming, GPS spoofing, lasers, EMP, projectile guns.

Question and answer: UPSC's provisional GS Paper I (2026, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 1 Oct 2026 (how we verify). Permalink · Report an error

Answer: (a) 1 and 2

The Su-30 MKI is built in India by Hindustan Aeronautics Limited at its Nasik division, and the T-90 Bhishma tank is built in India by Armoured Vehicles Nigam Limited, a Government of India enterprise. The Akula-class submarine the Navy has operated, INS Chakra, was a Russian-built boat taken on lease and is not Indian-made.

• ✓ 1. The Ministry of Defence's 2024 contract for 12 more Su-30MKI aircraft with HAL says they will be manufactured at HAL's Nasik division.
• ✓ 2. Armoured Vehicles Nigam Limited, a Government of India enterprise, lists the T90 Bhishma among the battle tanks in its own product range.
• ✗ 3. The Navy's Akula-class submarine, INS Chakra (ex-K-152 Nerpa), was handed over by the Russian Navy on a 10-year lease (The Times of India); India does not build Akula-class boats.

Remember · Su-30 MKI: built by HAL in India (Nasik). T-90 Bhishma: built by AVNL (Government of India enterprise). Akula-class submarine INS Chakra: leased from Russia, not Indian-built.

Question and answer: UPSC's provisional GS Paper I (2026, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 1 Oct 2026 (how we verify). Permalink · Report an error

Answer: (c) 1 and 2 only

The standard is IS 19445:2025, Bomb Disposal Systems: Performance Evaluation and Requirements, released on 24 December 2025. Its expected benefits include better interoperability of equipment across agencies. It was prepared by a BIS committee with a panel convened by TBRL (DRDO), with Indian stakeholders; no Russian institute is named.

• ✓ 1. IS 19445:2025 was released on National Consumer Day 2025 at Bharat Mandapam, New Delhi, as the Indian Standard for bomb disposal systems.
• ✓ 2. The official release lists improved reliability and interoperability of equipment across agencies among the standard's expected benefits.
• ✗ 3. The standard was developed by TBRL, Chandigarh (DRDO), and BIS at the Ministry of Home Affairs' request, through a BIS committee and a panel convened by TBRL. The official accounts name no Russian institute.

Remember · IS 19445:2025 is the BIS standard for bomb disposal systems (bomb blankets, baskets, inhibitors), developed by TBRL (DRDO) and BIS at the Home Ministry's request.

Question and answer: UPSC's provisional GS Paper I (2026, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (a) 1 and 3 only

Statements 1 and 3 are correct: REEs feed high-technology products such as magnets for EVs and wind turbines, and the National Critical Mineral Mission was launched in 2025. Statement 2 is wrong because China leads mining by a huge margin but India is far behind several other countries, and statement 4 is wrong because there are 17 rare earth elements, not 13.

• ✓ 1. Rare earth magnets are central to electric mobility, renewable energy, electronics and defence applications, and REEs such as dysprosium and neodymium go into wind-turbine magnets.
• ✗ 2. USGS shows China far ahead in 2025 mine production (270,000 tonnes REO), but India (2,900 tonnes) is well behind the United States (51,000), Australia, Burma and Thailand, so India is not second.
• ✓ 3. PIB records that the Government of India launched the NCMM in 2025 to build a robust framework for self-reliance in critical minerals (Cabinet approval was on 29 January 2025).
• ✗ 4. A Ministry of Mines/DAE reply in the Lok Sabha notes that REE has 17 elements, not 13.

Remember · There are 17 rare earth elements (15 lanthanides plus scandium and yttrium). NCMM was launched in 2025. China dominates mining; India is a minor producer.

Question and answer: UPSC's provisional GS Paper I (2026, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (c) I, II and III

Direct air capture (DAC) pulls CO2 straight out of ambient air. The captured CO2 can be stored underground, which removes it from the atmosphere, or used as a carbon feedstock for products such as food and beverages, chemicals and some plastics, and, combined with hydrogen, for synthetic aviation fuel. All three statements describe real uses.

• ✓ I Capturing CO2 from the air and storing it permanently removes it from the atmosphere; this is carbon removal by sequestration.
• ✓ II Air-captured CO2 can serve as a climate-neutral feedstock for a range of products, from food and beverages to chemicals, and some plastics are among the CO2-based products.
• ✓ III Air-captured CO2 combined with hydrogen is used to make synthetic hydrocarbon fuels, notably for aviation.

Remember · Direct air capture takes CO2 from ambient air: store it (carbon removal) or use it (food and beverages, chemicals, plastics, and synthetic fuels made with hydrogen).

Question and answer: UPSC's official GS Paper I (2025, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (c) All the three

An alternative powertrain vehicle is one driven by something other than a conventional internal combustion engine running on petrol or diesel. Battery-electric cars, hydrogen fuel-cell cars and fuel-cell hybrids that pair a fuel cell with an electric drive all fit, so all three are alternative powertrain vehicles.

• ✓ I A full battery electric vehicle has a battery charged from the grid and always operates in all-electric mode (US DOE Alternative Fuels Data Center); the World Bank lists battery electric vehicles among the alternative technologies countries are adopting.
• ✓ II A hydrogen fuel-cell vehicle is powered by hydrogen and produces no harmful tailpipe pollutants, unlike a conventional internal combustion engine vehicle; the World Bank treats it as another alternative to battery-powered vehicles.
• ✓ III A fuel cell-electric hybrid is built around a fuel cell supplying an electric motor, with a battery storing braking energy (US DOE), so it too replaces the conventional engine and counts as an alternative powertrain.

Remember · Alternative powertrains replace the conventional petrol/diesel engine: battery electric, hydrogen fuel cell and fuel cell-electric hybrid vehicles all count.

Question and answer: UPSC's official GS Paper I (2025, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 1 Oct 2026 (how we verify). Permalink · Report an error

Answer: (d) None

UAVs come in different designs with different abilities. Fixed-wing UAVs fly like aeroplanes and need a launcher and a landing device, while hovering and vertical take-off and landing belong to multirotor and hybrid VTOL types. Drones can also run on gasoline or hydrogen fuel cells, not only batteries. So none of the three 'all types' claims is correct.

• ✗ I Fixed-wing UAVs get lift from a rigid wing like an aeroplane and need launch infrastructure and a landing device; vertical landing is a feature of multirotor and VTOL types.
• ✗ II Hovering capability is one of the ways drones differ. Multirotors hover; fixed-wing UAVs, which rely on forward flight for lift, do not.
• ✗ III Battery power is only one option. Gasoline-powered drones give longer flight times, and fuel-cell (hydrogen) UAVs also exist, so not every UAV is battery-only.

Remember · UAV types differ: multirotor and VTOL can hover and land vertically, fixed-wing cannot; power may be battery, gasoline or hydrogen fuel cell.

Question and answer: UPSC's official GS Paper I (2025, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (b) These are explosives in military weapons

CL-20, HMX and LLM-105 are all high explosives, the kind packed into warheads and other military munitions. None of them is a refrigerant or a fuel; they release energy by detonating, not by burning steadily with oxygen from outside.

• ✓ (b) DRDO's High Energy Materials Research Laboratory, Pune, made CL-20 in the laboratory as a more powerful explosive than HMX, which fills most warheads. LLM-105 is also an explosive, an insensitive one whose performance lies between HMX and TATB.
• ✗ (c) Cruise missiles are propelled by ordinary fuels burnt in an engine. These three compounds sit in the warhead, not in the fuel tank.
• ✗ (a) Hydrofluorocarbon (HFC) refrigerants are gases used for cooling; these three are solid explosive compounds, so they have nothing to do with refrigeration.
• ✗ (d) Rocket propellants are designed to burn in a controlled way. These compounds are designed to detonate and are used as explosive fills.

Remember · CL-20 (most powerful of the three), HMX and LLM-105 (an insensitive explosive) are high-energy explosives for warheads, not fuels or refrigerants.

Question and answer: UPSC's official GS Paper I (2025, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (b) Only two

Two of the three pairs are correct. The Indian Coast Guard describes the Dornier-228 as a multi-mission maritime patrol aircraft, and the C-17 Globemaster III is a military transport, but the IL-76 is a strategic airlift aircraft, not a supersonic combat aircraft.

• ✓ I The Dornier-228 bought for the Indian Coast Guard is fitted with maritime patrol radar and an electro-optic infra-red device to strengthen aerial surveillance of maritime areas.
• ✗ II The IL-76 (Gajraj) is described by the Ministry of Defence as an Indian Air Force strategic airlift aircraft. It is a transporter, not a supersonic combat aircraft.
• ✓ III The C-17 Globemaster III was inducted into the Indian Air Force in 2013 to strengthen its strategic airlift.

Remember · Dornier-228: maritime patrol (Coast Guard). IL-76: strategic airlifter. C-17 Globemaster III: strategic military transport.

Question and answer: UPSC's official GS Paper I (2025, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 1 Oct 2026 (how we verify). Permalink · Report an error

Answer: (d) All four

Distributed energy resources (DER) are small generating or storage units placed close to where power is used, usually on the consumer's side of the meter, instead of large central power stations. Rooftop solar, home or grid batteries, small biomass generators and fuel cells are all standard examples.

• ✓ 1. Battery storage, including electric-vehicle batteries that can send power back to the grid, is listed by Australia's energy market rule-maker (AEMC) as a distributed energy resource.
• ✓ 2. Small biomass generators running on waste gas or farm and industrial by-products are a DER; the US EPA also lists biomass combustion among distributed generation options.
• ✓ 3. Fuel cells, run on natural gas, hydrogen or biomass-derived gas, produce electricity on site and are counted as distributed generation.
• ✓ 4. Rooftop solar PV is the most common DER: power is produced on the building that uses it, and surplus can be fed into the distribution grid.

Remember · DER = small, local generation or storage near the point of use: rooftop solar, small wind, batteries (incl. EVs), biomass generators, fuel cells, CHP units, mini-hydro.

Question and answer: UPSC's official GS Paper I (2024, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (b) 2 and 3 only

An RTG is not a reactor: nothing is split in a chain reaction. It simply turns the steady heat given off by the natural decay of plutonium-238 into electricity using thermocouples, which is why it powers deep-space probes and rovers such as Voyager, New Horizons, Curiosity and Perseverance. The US made its plutonium-238 at the Savannah River nuclear-materials plant, part of its weapons complex.

• ✗ 1. RTGs have no fission or chain reaction. Heat from the spontaneous radioactive decay of plutonium-238 is converted to power by thermocouples, with no moving parts.
• ✓ 2. They supply electricity and warmth to spacecraft where sunlight is weak or dust blocks solar panels; the current US model, the MMRTG, gives about 110 watts at launch.
• ✓ 3. Plutonium-238 is not weapons-grade plutonium, but the US produced it at its Savannah River plant, a site built to make nuclear-weapons materials, until the late 1980s; it is the standard RTG fuel.

Remember · RTG = heat from natural decay of Pu-238 → electricity via thermocouples (Seebeck effect). No fission. Powers Voyager, Cassini, New Horizons, Curiosity, Perseverance.

Question and answer: UPSC's official GS Paper I (2024, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 1 Oct 2026 (how we verify). Permalink · Report an error

Answer: (d) None

A fifth-generation fighter is built around stealth (low-observable shaping, weapons carried inside the body), fused sensor data and network-centric operations; Lockheed Martin describes the F-35 this way, and ADA lists the same features for India's own fifth-generation project, the AMCA. UPSC's key counts none of the three listed aircraft as fifth generation, and ADA's Tejas Mk-1 page lists fly-by-wire controls, a glass cockpit and a multi-mode radar, with external stores and drop tanks, and no stealth features.

• ✗ 1. The Rafale (printed 'Rafael') is a French twin-engine multirole fighter. UPSC's official key treats it as not fifth generation; we could not confirm its generation label from an official source, so we do not explain it here.
• ✗ 2. The MiG-29 is a Soviet-designed fighter. UPSC's official key treats it as not fifth generation; we could not confirm its generation label from an official source, so we do not explain it here.
• ✗ 3. ADA's page for Tejas Mk-1 lists relaxed static stability, fly-by-wire control, a glass cockpit and a multi-mode radar, with external stores and drop tanks; the low-observability shaping and internal weapons that ADA lists belong to the AMCA, India's own fifth-generation project.

Remember · Fifth-gen = stealth shaping + internal weapons + sensor fusion + networking (F-35, and India's AMCA). Tejas Mk-1 has none of the stealth features.

Question and answer: UPSC's official GS Paper I (2024, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 1 Oct 2026 (how we verify). Permalink · Report an error

Answer: (d) Water vapour

A hydrogen fuel cell combines hydrogen from the tank with oxygen from the air to produce electricity for the motor. The only chemical product of that reaction is water (H2O), so the tailpipe of a fuel-cell car releases just water vapour and some warm air, with no smog-forming pollutants.

• ✓ (d) At the cathode, the hydrogen ions, the electrons that have passed through the circuit and oxygen join to form water, which leaves as vapour.
• ✗ (c) Oxygen is consumed by the fuel cell, not given out; it is taken in from the air as a reactant.
• ✗ (a) Hydrogen peroxide (H2O2) is not a product of a fuel cell's hydrogen–oxygen reaction; the cell is designed to yield plain water.

Remember · Hydrogen fuel cell: 2H2 + O2 → 2H2O + electricity + heat. FCEV tailpipe emits only water vapour and warm air.

Question and answer: UPSC's official GS Paper I (2024, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (c) Long duration energy storage

Pumped-storage hydropower is a way of storing electricity, not of watering crops. When power is cheap or surplus (for example sunny afternoons with lots of solar), water is pumped from a lower reservoir to an upper one; when demand peaks, it is released back down through turbines. It can hold energy for many hours, which is why it is discussed as long-duration storage for a grid with more solar and wind.

• ✓ (c) Two reservoirs at different heights work like a giant rechargeable battery; pumped storage is the dominant form of grid-scale energy storage worldwide.
• ✗ (b) Lift irrigation also pumps water uphill, but only to deliver it to fields; nothing flows back through turbines to generate electricity.
• ✗ (d) Rainwater harvesting collects and stores rainwater for use or groundwater recharge; it has no power-generation or storage role.

Remember · Pumped-storage hydro = pump water up with surplus power, release it through turbines at peak demand. The biggest grid-scale storage technology; key for integrating solar and wind.

Question and answer: UPSC's official GS Paper I (2024, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (c) 1, 2, 3 and 4

Sustainable Aviation Fuel is made from renewable, non-petroleum feedstocks, and the US Department of Energy's list of them names all four materials: agricultural residues, corn grain, wet waste such as wastewater treatment sludge, and wood mill waste.

• ✓ 1. Agricultural residues are named on the DOE list of SAF feedstocks. They are a typical waste-based biomass source.
• ✓ 2. Corn grain is also on the list. It is a starch crop, which is why it feeds ethanol-based routes to jet fuel. ICAO's India study notes that maize supplies part of India's ethanol, and that ethanol can be turned into jet fuel by the alcohol-to-jet route.
• ✓ 3. Wet wastes, specifically manures and wastewater treatment sludge, are listed as feedstocks. ICAO's India study also mentions sewage sludge as a wet waste that can be turned into biocrude for SAF.
• ✓ 4. Wood mill waste is on the list. ICAO's India study lists sawdust and bark from sawmills among forest-based SAF feedstocks.

Remember · SAF feedstocks are broad: crops such as corn, crop and forest residues, wood mill waste, municipal solid waste, wet waste such as sludge, and fats, oils and greases.

Question and answer: UPSC's official GS Paper I (2024, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (c) Statement-I is correct but Statement-II is incorrect

Coal generates well over two-thirds of India's electricity even though the country has uranium ores, so Statement-I is right. Statement-II is wrong: India's heavy water reactors burn natural (unenriched) uranium and its light water reactors use only low-enriched uranium, nowhere near 60%.

• ✓ Statement-I Uranium occurs in India, for example in the Dharwar rocks and along the Singhbhum copper belt, but coal-fired plants still supply more than 70% of the electricity generated in the country.
• ✗ Statement-II Pressurised Heavy Water Reactors, the backbone of India's nuclear power, are fuelled by natural uranium, and Light Water Reactors by low-enriched uranium. Enrichment of 60% or more is not needed to produce electricity.

Remember · Coal: about 70–74% of India's electricity. PHWRs run on natural uranium; LWRs on low-enriched uranium. Power generation does not need highly enriched uranium.

📘 Read it in NCERT: Class 12 India: People and Economy, Ch 5 (practise this chapter)

Question and answer: UPSC's official GS Paper I (2023, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (d) Neither 1 nor 2

Neither statement is correct, because both swap the facts. Ballistic missiles are rocket-boosted and then coast on an arc, while cruise missiles fly under jet power. Agni-V is India's solid-fuelled intercontinental ballistic missile, and BrahMos is a supersonic cruise missile.

• ✗ 1. It is reversed. A ballistic missile has a short powered boost phase and then flies a mostly unpowered ballistic path, so it is not jet-propelled throughout. A cruise missile is normally powered by jet engines for most or all of its flight.
• ✗ 2. Again reversed. Agni-V is a three-stage solid-propellant Inter Continental Ballistic Missile with a range of over 5,000 km. BrahMos is a long-range supersonic cruise missile, launched from land, sea or air.

Remember · Ballistic: rocket boost, then unpowered arc. Cruise: jet-powered flight in the atmosphere. Agni-V is a solid-fuelled ICBM; BrahMos is a supersonic cruise missile.

Question and answer: UPSC's official GS Paper I (2023, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (c) All three

All three statements are correct. Green hydrogen is hydrogen made by splitting water with renewable electricity, and it is chemically the same fuel as any other hydrogen: it can burn in an engine, be mixed into natural gas, or feed a fuel cell.

• ✓ 1. Hydrogen internal combustion engines are in use: India's pilot projects under the National Green Hydrogen Mission include 22 hydrogen internal-combustion vehicles.
• ✓ 2. Hydrogen is already being blended into gas networks in India, for example up to 8% by volume in a piped natural gas network in Surat, for use as fuel.
• ✓ 3. Hydrogen fuel cells power vehicles; the same pilot projects include 15 fuel-cell vehicles, and hydrogen fuel-cell buses already run in Leh and Greater Noida.

Remember · Green hydrogen (made by electrolysis with renewable power) works as engine fuel, as a blend in natural gas, and in fuel cells for vehicles.

Question and answer: UPSC's official GS Paper I (2023, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (c) All three

All three. Green hydrogen, made by splitting water with renewable electricity, can replace the fossil-based hydrogen that fertilizer plants and refineries use today and the coal and coke that steel plants use for reducing iron ore. The Government of India names all three sectors in its National Green Hydrogen Mission.

• ✓ 1. Ammonia for nitrogenous fertilizers is made from hydrogen obtained from natural gas. Green hydrogen, or green ammonia made from it, can replace that and cut gas imports.
• ✓ 2. Refineries already use large amounts of hydrogen made from fossil fuels; swapping it for green hydrogen lowers a refinery's carbon footprint.
• ✓ 3. Hydrogen can replace coal and coke in iron and steel production, one of the biggest carbon-emitting industries; the Mission funds pilot projects for low-carbon steel.

Remember · Green hydrogen targets hard-to-abate sectors: fertilizer (green ammonia), refining, steel, and long-haul transport and shipping. India's mission aims at 5 MMT a year by 2030.

Question and answer: UPSC's official GS Paper I (2023, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (b) 1, 2 and 4 only

Monazite is a phosphate mineral of the beach sands that carries both rare earth elements and thorium. Because of the thorium, it is a 'prescribed substance' under the Atomic Energy Act, 1962, so only government entities licensed by the Department of Atomic Energy handle it. It is concentrated on particular stretches of coast, not all of it.

• ✓ 1. Monazite is one of the world's principal economic sources of rare earth elements, along with bastnasite and loparite.
• ✓ 2. Monazite contains thorium; India's thorium comes mainly from monazite in the beach sands of Kerala and Tamil Nadu.
• ✗ 3. Monazite-bearing sands occur along particular stretches of the peninsular coast (notably Kerala, Tamil Nadu and Odisha), not along the entire Indian coastline.
• ✓ 4. The Department of Atomic Energy has licensed no private entity to produce, process or export monazite; the public sector IREL (India) Limited handles it.

Remember · Monazite: beach-sand mineral with rare earths + thorium; 'prescribed substance' under the Atomic Energy Act, 1962; handled only by government entity IREL; richest deposits in Kerala.

📘 Read it in NCERT: Class 12 India: People and Economy, Ch 5 (practise this chapter)

Question and answer: UPSC's official GS Paper I (2022, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (b) Some use imported uranium and others use domestic supplies

The dividing line is the fuel: India's reactors that run on imported fuel are under IAEA safeguards, while those fuelled by India's own (indigenous) supplies are outside them. This follows the Separation Plan, notified under India's India-specific Safeguards Agreement with the IAEA, which covers only the civilian facilities India listed.

• ✓ (b) In a 2015 reply to the Lok Sabha, the Government said 13 reactors (Tarapur 1&2, Rajasthan 1 to 6, Kakrapar 1&2, Narora 1&2 and Kudankulam 1) are under IAEA Safeguards and use imported fuel, while the other eight, such as Kaiga 1 to 4, run on indigenous fuel.
• ✗ (c) Ownership or operator is not the divider: Tarapur Units 1&2 are safeguarded, but Tarapur Units 3&4 at the same station, fuelled by indigenous fuel, are not.
• ✗ (a) Official statements draw the line between imported and indigenous fuel, not between uranium and thorium.

Remember · Indian power reactors that use imported fuel (e.g. Tarapur 1&2, Kudankulam) are under IAEA safeguards; those on indigenous fuel (e.g. Kaiga, Madras, Tarapur 3&4) are not.

Question and answer: UPSC's official GS Paper I (2020, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (b) 2 and 3 only

Statements 2 and 3 are correct. Blending hydrogen, which has no carbon, into CNG lowers carbon dioxide and hydrocarbon emissions, and India's trials and rules use a blend of about 18% hydrogen by volume, which is within one-fifth. H-CNG does not eliminate carbon monoxide and is not cheaper than plain CNG.

• ✗ 1. H-CNG is still mostly natural gas, a carbon fuel, so it can lower carbon monoxide but cannot eliminate it. Official pages describe the benefit as emissions reduction, not elimination.
• ✓ 2. Part of the fuel is carbon-free hydrogen, so less carbon is burnt per unit of energy and the blend gives lower carbon dioxide and hydrocarbon emissions; the Petroleum Ministry calls H-CNG an interim technology for emissions reduction.
• ✓ 3. The Road Transport Ministry allowed H-CNG with an 18% hydrogen mix in CNG engines, which is under one-fifth (20%) by volume; the Delhi bus trials also used 18%.
• ✗ 4. Making the blend is costly: the Petroleum Ministry notes that the high cost of producing and blending hydrogen offsets the fuel-economy savings over plain CNG, and its Secretary called commercial viability the main challenge.
• • Since then After the exam year, the Road Transport Ministry notified (GSR 585(E), 25 September 2020) H-CNG with an 18% hydrogen mix as an automotive fuel.

Remember · H-CNG is CNG blended with up to about 18% hydrogen by volume: it lowers emissions but does not remove them, and it is costlier than plain CNG.

Question and answer: UPSC's official GS Paper I (2019, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (b) Russia

India signed this Action Plan with Russia during President Vladimir Putin's visit to New Delhi for the 19th annual summit, on 5 October 2018. It was signed by Rosatom, Russia's state atomic energy corporation, and India's Department of Atomic Energy.

• ✓ (b) The India-Russia Joint Statement of 5 October 2018 records satisfaction over the signing of this Action Plan. The official list of agreements shows Rosatom's Director General and the Secretary, Department of Atomic Energy, as signatories.
• ✗ (a) The action plan was signed with Russia, not Japan.
• ✗ (c) The action plan was signed with Russia, not the United Kingdom.
• ✗ (d) The action plan was signed with Russia, not the USA.

Remember · Action Plan for Prioritization and Implementation of Cooperation Areas in the Nuclear Field: India-Russia, signed 5 October 2018 (Putin's visit), between Rosatom and India's DAE.

Question and answer: UPSC's official GS Paper I (2019, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (a) 1 only

The NSG is an informal club of nuclear supplier countries that coordinates export controls, so joining it eases a country's access to nuclear trade and technology. It is not a treaty body, and joining it does not by itself make a country a party to the NPT.

• ✓ 1. NSG participants shape and share the rules of nuclear trade among the main supplier states, which gives them easier access to advanced nuclear technology and equipment.
• ✗ 2. The NSG was not created by a treaty; it is a voluntary, non-legally binding association. NPT membership comes only by signing and ratifying the NPT itself.

Remember · NSG: voluntary supplier-country group formed 1975 after India's 1974 test; controls nuclear and dual-use exports through two sets of Guidelines; not a treaty, so membership does not mean NPT membership.

Question and answer: UPSC's official GS Paper I (2018, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (a) The civilian nuclear reactors come under IAEA safeguards.

India's Additional Protocol is attached to its India-specific safeguards agreement with the IAEA, which covers only India's civilian nuclear facilities. So ratifying it means those civilian facilities stay under IAEA safeguards and get wider IAEA access; military installations are left out.

• ✓ (a) The IAEA Board approved a safeguards agreement with India in 2008 for the application of IAEA safeguards to Indian civilian nuclear facilities. The Additional Protocol to that agreement entered into force on 25 July 2014.
• ✗ (b) Both the safeguards agreement and its Additional Protocol are titled as covering 'Civilian Nuclear Facilities'. India's military installations are not placed under IAEA inspection.
• ✗ (c) The Additional Protocol is an arrangement with the IAEA. It does not give India any right to buy uranium from the Nuclear Suppliers Group, which is a separate body.
• ✗ (d) Ratifying a protocol with the IAEA does not make a country a member of the NSG. NSG membership is a separate matter decided within that group.

Remember · India's Additional Protocol (signed 15 May 2009; in force 25 July 2014) extends IAEA safeguards access to its civilian nuclear facilities only.

Question and answer: UPSC's official GS Paper I (2018, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (c) An American anti-missile system

THAAD is an American anti-missile system. It is a land-based system of the US Missile Defense Agency and US Army that destroys ballistic missiles in their final (terminal) phase of flight, using hit-to-kill interceptors.

• ✓ (c) THAAD batteries have a launcher, interceptors, an AN/TPY-2 radar and fire control. They are procured and fielded to the US Army, and the interceptor destroys the warhead by direct impact.
• ✗ (b) India's own anti-missile effort is the Ballistic Missile Defence programme of DRDO, which flight-tests indigenous interceptors. It is a separate programme from THAAD.
• ✗ (a) THAAD is developed and fielded by the United States (US Missile Defense Agency and US Army), not by Israel, and it is an interceptor system rather than only a radar.
• ✗ (d) THAAD is fielded to the US Army to protect US forces and allies. It is not a joint Japan–South Korea defence arrangement.

Remember · THAAD = Terminal High Altitude Area Defense: a US ground-based, hit-to-kill system against ballistic missiles in their terminal phase. India's own shield is DRDO's BMD.

Question and answer: UPSC's official GS Paper I (2018, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (b) 2 and 3 only

Algae for fuel are grown on land, in open ponds or closed photobioreactors, often on non-arable land with non-potable water, so statement 1 is false. The real hurdles for a developing country are the engineering know-how needed and the very large scale (land, water, nutrients, CO2) needed to make it pay.

• ✗ 1. Algae are cultivated on land in open raceway ponds, attached-growth systems and closed photobioreactors; non-arable land is listed as one of the resources for growing them.
• ✓ 2. Designing cultivation systems that keep resource use and costs low while keeping productivity high, and then harvesting and processing the biomass, needs advanced technology and skills.
• ✓ 3. An algal biofuel industry has to scale up to use a large amount of land, water, nutrients and CO2, which can compete with other uses and raise ecological and social concerns.

Remember · Algal (third-generation) biofuel: grown on land in ponds or photobioreactors, even on non-arable land with saline or waste water; the limits are technology and the scale needed to be viable.

Question and answer: UPSC's official GS Paper I (2017, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (d) 1, 2 and 3

Geological carbon storage injects captured CO2 deep underground into porous rock sealed by an impermeable cap. Saline formations, oil and gas reservoirs and unmineable coal seams are all standard candidate sites, so all three are correct.

• ✓ 1. Coal that cannot be mined economically can adsorb CO2 on its surfaces; unmineable coal seams are one of the formation types studied for storage.
• ✓ 2. Oil and gas reservoirs held fluids for millions of years under a sealing layer, so once depleted they can hold injected CO2; injection can also push out extra oil.
• ✓ 3. Deep saline formations (porous rock filled with brine) have the largest storage capacity and are the main target for large-scale storage.

Remember · Geological CO2 storage sites: deep saline formations, depleted oil and gas reservoirs, unmineable coal seams (also organic-rich shales and basalt).

Question and answer: UPSC's official GS Paper I (2017, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (d) Neither 1 nor 2

The Nuclear Security Summits were a US-initiated series of leaders' meetings (2010–2016), not a UN process, and the International Panel on Fissile Materials is an independent group of experts, not part of the IAEA. Both statements are wrong.

• ✗ 1. The summit process was announced by US President Barack Obama in April 2009. Four summits were held (Washington 2010, Seoul 2012, The Hague 2014, Washington 2016), hosted by those countries, not by the UN.
• ✗ 2. The IPFM was founded in January 2006 as an independent panel of experts drawn from countries with and without nuclear weapons; it studies fissile material policy and is not part of the IAEA.

Remember · Nuclear Security Summits: Obama's initiative, four summits 2010–2016, outside the UN. IPFM (2006): independent expert panel on fissile material, not an IAEA body.

Question and answer: UPSC's official GS Paper I (2017, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error