General & Miscellaneous — UPSC Prelims Science & Environment previous year questions

Statement 1 is wrong. The Deep Ocean Mission was launched by the Ministry of Earth Sciences, not the Ministry of Ports, Shipping and Waterways.
Statement 2 is correct. Matsya-6000 is a crewed submersible designed to carry three people to a depth of 6,000 metres.
Statement 3 is correct. Samudrayaan is the project under the Mission to send humans into the deep sea.
So 2 and 3 only.
Remember: the mission is the Ministry of Earth Sciences' blue economy effort and is developed with NIOT.

Source: Ministry of Earth Sciences, Deep Ocean Mission; NIOT Chennai

The 2025 Nobel Prize in Physics went to John Clarke, Michel Devoret and John Martinis for quantum tunnelling in an electric circuit.
John Clarke was born in Cambridge, UK, and was a professor at the University of California, Berkeley when the prize was announced. He fits the clues.
Michel Devoret was born in France. Richard Robson won the Chemistry prize but worked in Australia. Joel Mokyr won the Economics prize and was born in the Netherlands.
So X is John Clarke.
Remember: the 2025 Chemistry prize was for metal-organic frameworks.

Source: Nobel Prize official website, 2025 laureates

Statement 1 is correct. The Bharat Forecast System is a high-resolution weather model. It aims to give forecasts at the level of a cluster of panchayats.
Statement 2 is wrong. It was developed by the Indian Institute of Tropical Meteorology, Pune, under the Ministry of Earth Sciences. It was not developed by IIT Delhi.
So 1 only.
Remember: higher resolution means a smaller grid size, so forecasts are more local.

Source: Ministry of Earth Sciences; IITM Pune press releases

All three are alternative powertrain vehicles.
An alternative powertrain is a drive system that does not rely only on a petrol or diesel engine.
Full battery electric vehicles run on stored electricity. Hydrogen fuel cell vehicles make electricity on board from hydrogen. Fuel cell-electric hybrids combine a fuel cell with a battery.
So the answer is all the three.
Remember: Plug-in hybrids and gas-fuelled vehicles are also usually counted as alternative powertrains.

Source: Ministry of Heavy Industries, FAME and PLI-Auto scheme documents; NITI Aayog report on electric mobility

The question asks for the statements that are not correct.
Statement I is not correct. The National Rail Plan aims at a future-ready railway system by 2030, not 2028.
Statement II is not correct. Kavach is an indigenous Automatic Train Protection system. RDSO developed it with Indian industry. It was not developed with Germany.
Statement III is correct. Kavach uses RFID tags fitted on the track in station sections.
So I and II are the statements that are not correct. Option (a) fits.
Remember: Kavach is built to the Safety Integrity Level 4 (SIL-4) standard.

Source: Ministry of Railways and RDSO material on Kavach; National Rail Plan (2021)

Pumped-storage hydropower uses two water reservoirs at different heights. When power is cheap, water is pumped up to the upper reservoir. When power is needed, water runs down through turbines to make electricity.
It stores energy for many hours, so it is long duration energy storage. It helps balance solar and wind power.
It has nothing to do with irrigation of terraces, lift irrigation or rainwater harvesting.
Remember: a pumped-storage plant works like a giant water battery.

Source: Central Electricity Authority and Ministry of Power guidelines on pumped storage projects

Statement 1 is correct. Hydrogen can be burnt in an internal combustion engine.
Statement 2 is correct. Hydrogen can be blended with natural gas in limited proportion for heating or power.
Statement 3 is correct. A fuel cell turns hydrogen into electricity and runs electric vehicles.
Green hydrogen is hydrogen made by splitting water with renewable electricity.
Remember: India's National Green Hydrogen Mission was approved in January 2023.

Source: National Green Hydrogen Mission, MNRE / PIB

The Polar Code is the International Code for Ships Operating in Polar Waters.
It was adopted by the International Maritime Organization (IMO) and is in force since 1 January 2017.
It covers ship design, equipment, crew training and environmental protection in the Arctic and Antarctic.
Option 2 is wrong because the Code does not settle territorial claims.
Option 3 is wrong because it does not regulate scientific research.
Option 4 is wrong because it is not a trade or security pact.
Remember: The Polar Code works under SOLAS and MARPOL.

Source: International Maritime Organization, International Code for Ships Operating in Polar Waters (Polar Code)

Statement 1 is correct. The Climate-Smart Village approach in India is part of the CCAFS research programme.
Statement 2 is correct. CCAFS works under the CGIAR. CGIAR is headquartered in Montpellier, France.
Statement 3 is correct. ICRISAT, at Patancheru near Hyderabad, is a CGIAR research centre.
So all three statements are correct.

Source: CGIAR / CCAFS; ICRISAT

Denisovans are an extinct group of archaic humans. They lived in Asia during the Pleistocene.
Their remains were first identified from a finger bone found in Denisova Cave, Siberia, in 2010.
DNA tests showed they were related to Neanderthals but distinct from them.
Option a is wrong because they are not dinosaurs. Option c is wrong because Denisova Cave is in Siberia, not North-East India. Option d is wrong because they are not a geological period.
Remember: Denisovan DNA is found in present-day populations of Oceania and South-East Asia.

Source: Standard references on human evolution; Denisova Cave finds (Siberia, Russia)

Pair 1 is correct. Lipsticks can contain traces of lead as an impurity in pigments.
Pair 2 is correct. Brominated vegetable oil is used in some soft drinks to keep flavour oils mixed. It is controversial and banned in several countries.
Pair 3 is correct. Monosodium glutamate is a flavour enhancer widely used in Chinese-style fast food. Its safety in large amounts is debated.
So all three pairs are correctly matched.
Remember: MSG is also sold as 'ajinomoto'.

Source: FSSAI and US FDA information on lead in cosmetics, brominated vegetable oil and monosodium glutamate

These are concepts of theoretical physics and cosmology.
An event horizon is the boundary around a black hole beyond which nothing can escape.
A singularity is a point of infinite density at the centre of a black hole.
String theory tries to explain all forces and particles as tiny vibrating strings.
The Standard Model describes the known elementary particles and three of the four forces.
They have no link with eclipses, satellite launch or biological evolution.
Remember: all four terms deal with the structure of the Universe.

Source: Standard physics references on cosmology

Statement 1 is correct. IceCube watches a cubic kilometre of Antarctic ice for neutrinos.
Statement 2 is correct. It also searches for signs of dark matter through the neutrinos it may produce.
Statement 3 is correct. Its sensors are buried between 1.5 and 2.5 km deep in the ice.
Remember: neutrinos are nearly massless particles that rarely interact with matter.

Source: IceCube Neutrino Observatory, University of Wisconsin-Madison

A is matched with 2. Raja Ramanna was a nuclear physicist who led India's first nuclear test team in 1974.
B is matched with 5. M.S. Swaminathan is known for agricultural science and the Green Revolution.
C is matched with 4. U.R. Rao was a space scientist and a former ISRO chairman.
D is matched with 3. Meghnad Saha worked on thermal ionisation, which is used in astrophysics.
No scientist here works in plant chemistry, so option 1 is not used in the correct code.
Remember: Saha's ionisation equation explains the spectra of stars.

Source: Standard biographical record of Indian scientists; ISRO and DAE profiles

The Forest Research Institute is at Dehradun, so A matches 3.
The Indian Grassland and Fodder Research Institute is at Jhansi, so B matches 4.
The Central Arid Zone Research Institute is at Jodhpur, so C matches 1.
The Indian Agricultural Research Institute is at New Delhi, so D matches 2.
This gives the code 3 4 1 2.
Remember: IARI is also called the Pusa Institute.

Source: ICFRE and ICAR institute profiles

A-3: Minerals are exhaustible. They take millions of years to form.
B-4: Solar energy is inexhaustible. The Sun will supply it for billions of years.
C-2: Biogas is mainly methane and carbon dioxide.
D-1: Deforestation reduces rainfall by cutting transpiration.
So the code is 3, 4, 2, 1.
Remember: Biogas is about 55-65 percent methane.

Source: NCERT Class XI Geography, India: People and Economy; NCERT Class XII Biology, Environmental Issues

A cusec is a unit for rate of flow of water, so A matches 3.
A byte is a unit of computer data, so B matches 4.
The Richter scale gives the earthquake size, so C matches 2. Strictly, it measures magnitude; the question calls it intensity.
A bar is a unit of pressure, so D matches 1.
The correct code is 3 4 2 1.
Remember: Magnitude is measured by the Richter scale. Intensity is measured by the Mercalli scale.

Source: Standard units of measurement; NCERT Class XI, Fundamentals of Physical Geography, Ch. 3 (Earthquakes)

A stethoscope is used to hear heart sounds. So A matches 3.
A sphygmomanometer measures blood pressure. So B matches 4.
A caratometer checks the purity of gold in carats. So C matches 2.
A luxmeter measures the intensity of light. So D matches 1.
Remember: Gold purity is measured in carats, with 24 carat being pure.

Source: Standard physics and instrumentation texts

Assertion (A) is correct. A black hole gives out no light, so a telescope cannot see it directly.
Reason (R) is correct. Inside the event horizon, the pull of gravity is so strong that even light cannot escape.
R explains A, because without light there is nothing for a telescope to detect.
Scientists detect black holes only by their effect on nearby stars and gas.
Remember: The boundary beyond which light cannot escape is the event horizon.

Source: NASA, introduction to black holes; NCERT Class XI Physics, gravitation

Koyna is a well-known case of reservoir-induced seismicity.
The Koyna dam stands on an old fault in the Deccan Plateau.
When the water level rises or falls, pore pressure in the rocks changes. This can reactivate the fault and trigger earthquakes.
So (R) is true and it explains why the region stays quake-prone, which is (A).
Option (b) is wrong because (R) directly gives the mechanism. Options (c) and (d) are wrong because both statements are true.
Remember: The 1967 Koyna earthquake was one of the strongest reservoir-induced earthquakes recorded.

Source: Geological Survey of India / NCERT Class XI, Fundamentals of Physical Geography (earthquakes)