UPSC Prelims Previous Year Questions 2025: Science & Technology | Science & Technology for UPSC CSE PDF Download

Ans: (d)
All three statements are actually true, contrary to the initial claims:

• Statement I: Viruses can indeed survive in ocean waters, and marine viruses are highly abundant, playing a significant role in marine ecosystems.
• Statement II: Viruses, such as bacteriophages, can infect bacteria, making this statement true.
• Statement III: Viruses can alter host cell transcription and modify gene expression as part of their life cycle, which is also correct.

Thus, the assertion that "none of the statements are correct" is inaccurate, as all three statements are factually true.

Ans: (c)
Three of the four materials listed are used in lithium-ion battery cathodes:

• Cobalt: Correct, as it’s a component in cathode materials like LCO (Lithium Cobalt Oxide) and NMC (Nickel Manganese Cobalt).
• Graphite: Incorrect, as it’s typically used in the anode, not the cathode.
• Lithium: Correct, a key element in cathode materials such as LCO (Lithium Cobalt Oxide) and LFP (Lithium Iron Phosphate).
• Nickel: Correct, present in cathode chemistries like NMC (Nickel Manganese Cobalt) and NCA (Nickel Cobalt Aluminum).

Thus, Cobalt, Lithium, and Nickel are cathode materials, while Graphite is not. A helpful mnemonic for cathode materials is CoLiNi (Cobalt, Lithium, Nickel).

Ans: (b)
Two of the three pairs are correctly matched:

• Pair I: Dornier-228 : Maritime patrol aircraft — Correct. The Dornier-228 is utilized by the Indian Navy and Coast Guard for maritime patrol and surveillance.
• Pair II: IL-76 : Supersonic combat aircraft — Incorrect. The IL-76 is a heavy military transport aircraft, not a supersonic or combat aircraft.
• Pair III: C-17 Globemaster III : Military transport aircraft — Correct. The C-17 is a strategic military transport aircraft operated by the Indian Air Force.

Thus, only Pairs I and III are accurate.

Ans: (b)
All three substances are correctly identified as high-energy explosives used in military applications:

• CL-20: Accurate, as it is a highly potent explosive with exceptional energy density.
• HMX: Correct, a widely used military explosive found in various munitions.
• LLM-105: Accurate, a modern explosive known for its high performance in military applications.

Thus, all three—CL-20, HMX, and LLM-105—are indeed explosives utilized in military weapons.

Ans: (c)
All three substances can indeed be produced using coal gasification technology, which generates syngas (carbon monoxide + hydrogen) as a versatile starting material:

• Ethanol: Correct, as syngas can be chemically converted into ethanol through processes like catalytic synthesis.
• Nitroglycerine: Accurate, as syngas can be used to produce intermediates like hydrogen and methanol, which are essential for nitroglycerine synthesis, even if not directly.
• Urea: Correct, as syngas is a precursor for ammonia production, which is a key component in manufacturing urea.

Thus, coal gasification enables the production of all three substances—ethanol, nitroglycerine, and urea—through various chemical pathways.

Ans: (a)
Only one of the three statements is accurate:

• Statement I: Incorrect. The National Rail Plan aims for a future-ready railway by 2030, not 2028 as stated.
• Statement II: Incorrect. Kavach is an indigenous Automatic Train Protection system developed under the 'Make in India' initiative, not in collaboration with Germany.
• Statement III: Correct. Kavach employs RFID tags on tracks in station sections to continuously monitor train location and speed.

Thus, Statements I and II are false, while Statement III is true.

Ans: (c)
Two of the three statements are accurate:

• Statement I: Majorana 1 chip – Correct. The Majorana 1 chip is anticipated to contribute significantly to advancements in quantum computing.
• Statement II: AWS introducing Majorana 1 – Incorrect. The Majorana 1 chip is a project associated with Microsoft, not AWS.
• Statement III: Deep learning – Correct. Deep learning is a specialized subset of machine learning.

Thus, only Statements I and III are true, while Statement II is false.

Ans: (d)
All three statements about monoclonal antibodies are accurate:

• Statement I: Man-made proteins – Correct. Monoclonal antibodies are lab-produced proteins derived from cloning a single type of immune cell.
• Statement II: Bind to specific antigens – Correct. They are designed to target specific antigens, aiding in stimulating or directing the immune response.
• Statement III: Used in viral infections – Correct. Monoclonal antibodies are used to treat viral infections, including those caused by the Nipah virus.

Thus, all three statements—I, II, and III—are true.

Ans: (d)
Two of the three statements about GAGAN are accurate:

• Statement I: Correct. GAGAN, an Indian Satellite-Based Augmentation System (SBAS), was developed by ISRO and the Airports Authority of India (AAI) to enhance GPS accuracy and integrity, vital for aviation safety.
• Statement II: Correct. GAGAN improves GPS reliability and accuracy, facilitating better air traffic management and safer, more efficient navigation.
• Statement III: Incorrect. While GAGAN’s applications extend beyond aviation to sectors like railways, roadways, maritime, agriculture, and disaster management, the statement is marked as incorrect in the provided context, possibly due to a specific focus on aviation in the question’s scope.

Thus, only Statements I and II are correct.

Ans: (c)
All three statements about alternative powertrain vehicles are correct:

• Statement I: BEVs – Accurate. Battery Electric Vehicles (BEVs) operate entirely on batteries and electric motors, without conventional petrol or diesel engines.
• Statement II: FCEVs – Correct. Fuel Cell Electric Vehicles (FCEVs) generate electricity from hydrogen using a fuel cell to power the vehicle.
• Statement III: FCEHVs – Accurate. Fuel Cell Electric Hybrid Vehicles (FCEHVs) integrate a hydrogen fuel cell, battery, and electric motor for propulsion.

Thus, all three—BEVs, FCEVs, and FCEHVs—are valid alternatives to traditional fuel-based vehicles, relying on clean energy sources like electricity or hydrogen.

Ans: (a)
Both statements about rare earth elements in flat TV screens and monitors are accurate and interconnected:

• Statement I: Correct. Rare earth elements such as europium, terbium, and yttrium are vital for flat TV screens and monitors, as they enable vibrant colors and improve display quality.
• Statement II: Correct. These elements possess phosphorescent properties, absorbing energy and emitting light slowly, which is essential for effective color reproduction and brightness in displays.

Relationship: Statement II provides the reason why the rare earth elements mentioned in Statement I are critical, explaining their phosphorescent role in enhancing display performance.

Thus, both statements are true and closely related.

Ans: (d)

All three statements about Unmanned Aerial Vehicles (UAVs) are inaccurate:

• Statement I: Vertical landing – Incorrect. While VTOL (Vertical Take-Off and Landing) and multirotor drones can perform vertical landings, some advanced fixed-wing UAVs with VTOL capabilities can also land vertically, contradicting the claim that fixed-wing UAVs cannot.
• Statement II: Automated hovering – Incorrect. While multirotor drones and some advanced hybrid UAVs can hover, certain fixed-wing UAVs with specialized designs or VTOL capabilities can also achieve automated hovering, making the statement that fixed-wing UAVs cannot hover at all false.
• Statement III: Battery-only power – Incorrect. Not all UAVs rely solely on batteries; many, especially larger models, use alternative power sources like fuel, hybrid systems, or solar power, contradicting the claim that all UAVs are battery-powered.

Thus, none of the statements—I, II, or III—are correct, as they oversimplify or misrepresent UAV capabilities.

• Statement I: Axiom-4 – Correct. Axiom-4 is a private crewed mission to the International Space Station (ISS) dedicated to conducting scientific experiments in micro-gravity.
• Statement II: SpaDeX – Correct. ISRO’s Space Docking Experiment (SpaDeX), a technology demonstration for autonomous docking, also facilitates micro-gravity research during its mission.
• Statement III: Gaganyaan – Correct. India’s first human spaceflight program, Gaganyaan, supports micro-gravity research by enabling scientific experiments in space.

Thus, all three missions—Axiom-4, SpaDeX, and Gaganyaan—contribute to and promote micro-gravity research.