UPSC Prelims 2025 Analysis

Explanation

Oxygen on Earth mainly comes from photosynthesis, especially by phytoplankton (marine organisms), and oxygen levels differ between air and water.

❌ Statement I is incorrect:

• Oceans (phytoplankton) produce more oxygen than rainforests.

✅ Statement II is correct:

• Marine phytoplankton and photosynthetic bacteria produce about 50% of the world’s oxygen.

❌ Statement III is incorrect:

• Atmospheric air has much more oxygen than surface water; water does not contain several folds higher oxygen than air.

So, the correct answer is: B

Explanation

Article 6 of the Paris Agreement is crucial as it outlines international cooperation through both carbon markets and non-market approaches to help countries meet climate goals.

✅ Statement I is correct:

• Article 6 is widely discussed because it enables cooperation through market and non-market means to fight climate change.

✅ Statement II is correct:

• It defines rules for carbon markets, including carbon trading and credit mechanisms.

✅ Statement III is correct:

• It also promotes non-market tools like technology transfer and capacity building to reach climate targets.

So, the correct answer is: A

Explanation

At COP28, India chose not to sign the “Declaration on Climate and Health,” and this decision can be understood by analyzing the nature of the declaration and India’s concerns.

✅ Statement I: Correct. India did not sign the COP28 Declaration on Climate and Health, unlike over 120 other countries.

❌ Statement II: Incorrect. The declaration is not legally binding; it is a voluntary political commitment. Signing it does not legally mandate countries to decarbonize their health sectors immediately.

✅Statement III: Correct. India’s concern is that rapid decarbonization of its health sector could compromise the resilience and accessibility of healthcare services, given current developmental challenges and resource constraints.

Therefore, only Statement III correctly explains Statement I, while Statement II is factually wrong about the binding nature of the declaration.

Explanation

The Peacock tarantula (Gooty tarantula) is a rare, tree-dwelling spider found in limited forest areas in India.

❌ Statement I is incorrect:

• It is a spider (arachnid), not an omnivorous crustacean.

✅ Statement II is correct:

• Its habitat is restricted to some forest areas in the Eastern Ghats.

✅ Statement III is correct:

• It is arboreal, living in trees and tree crevices.

So, the correct answer is: D

Explanation

Nature-based solutions involve using natural processes to tackle climate change and biodiversity loss, often needing dedicated financial support.n ADB launched the Nature Solutions Finance Hub for Asia and the Pacific to fund nature-based solutions for climate and environmental challenges in the region.

Explanation

✅ A. silver iodide and potassium iodide: True Both are used in cloud seeding because their crystalline structures help form ice nuclei, inducing rainfall.

❌ B. silver nitrate and potassium iodide: False Silver nitrate is not used for artificial rainmaking.

❌ C. silver iodide and potassium nitrate: False Potassium nitrate is not used in cloud seeding.

❌ D. silver nitrate and potassium chloride: False Neither chemical is used in artificial rainmaking.

Therefore, option A is correct.

Explanation

Activated carbon is widely used to clean pollutants because of its unique properties and sustainable production methods.

✅ Statement I: Correct. Activated carbon effectively removes pollutants from industrial effluents due to its high adsorption capacity. It’s commonly used in water treatment and pollution control. ✅Statement II: Correct. This is because activated carbon has an extremely large surface area, created by its porous structure, allowing it to trap heavy metals and other contaminants efficiently. ✅ Statement III: Correct. Moreover, activated carbon can be produced easily and cost-effectively from carbon-rich wastes like coconut shells, rice husks, and other agricultural residues, making it an eco-friendly option.

Thus, both Statement II and Statement III are correct, and together they explain why Statement I is true.

Explanation

India’s CO₂ emissions come mainly from fuel combustion, especially electricity generation, and per capita emissions are higher than 0.5 tonnes.

❌ Statement I is incorrect:

• India’s per capita CO₂ emissions are around 1.9-2.0 tonnes, higher than 0.5 t CO₂/capita.

✅ Statement II is correct:

• India ranks second in the Asia-Pacific for total CO₂ emissions from fuel combustion, after China.

✅ Statement III is correct:

• Electricity and heat production (mainly coal-based) is the largest source of India’s CO₂ emissions.

So, the correct answer is: C

Explanation

✅ A. The European Union: The Nature Restoration Law (NRL) is an EU legislative initiative adopted in 2024. It sets binding targets to restore ecosystems, fight climate change, and protect biodiversity across EU member states.

❌ B. The World Bank: An international financial institution providing loans and grants; it does not enact laws like the NRL.

❌ C. OECD: An organization promoting economic cooperation and policy coordination; it does not enact binding environmental laws such as the NRL.

❌ D. FAO: A UN agency focused on hunger and agriculture; it does not enact regional laws like the NRL.

Explanation

Wet-bulb temperature combines heat and humidity. When it exceeds 35°C, the human body can no longer cool itself through sweating, posing a serious threat to survival.

❌ Statement I: Incorrect

• Though flooding, cyclones, and droughts are valid climate threats, they are not directly related to the World Bank's warning about wet-bulb temperatures.

✅ Statement II: Correct

• When wet-bulb temperatures cross 35°C, the body cannot release heat, making it fatal for humans and animals.

Explanation

Many everyday items contain hidden plastics, even if they don’t look like typical plastic products.

• ✅I. Cigarette butts – Filters are made of cellulose acetate, a form of plastic.
• ✅II. Eyeglass lenses – Usually made from polycarbonate or CR-39 plastic, not glass.
• ✅III. Car tyres – Contain synthetic rubber, which includes plastic-based polymers.

All three items contain plastic.

Explanation

A circular economy focuses on minimizing waste, reusing resources, and improving efficiency, all of which help lower greenhouse gas emissions and conserve raw materials.

✅ Statement I: Correct By reducing waste and energy use, the circular economy helps cut greenhouse gas emissions.

✅ Statement II: Correct It reduces the need for raw materials through reuse, recycling, and product life extension.

✅ Statement III: Correct It also lowers production waste using efficient and sustainable design and processes.

Explanation

Cement manufacturing contributes significantly to global carbon emissions, mainly due to the chemical process involved in producing clinker.

✅ Statement I: Cement industry emissions are estimated to be around 5-8% of global CO₂ emissions, making it a major source of greenhouse gases. ✅Statement II: Silica-bearing clay is indeed mixed with limestone during cement making to provide essential minerals like silicon, aluminum, and iron needed for the final product. ✅Statement III: During clinker production, limestone (calcium carbonate) is heated and converted into lime (calcium oxide), releasing CO₂ in the process. This calcination is the main source of carbon emissions in cement manufacturing.

Both Statements II and III are correct, but only Statement III directly explains the source of carbon emissions mentioned in Statement I.

Explanation

Plants can be classified based on their growth form — woody shrubs, herbs with pseudostems, climbers, etc.

✅ I. Cassava : Woody shrub — Correct

• Cassava is a perennial woody shrub.

✅ II. Ginger : Herb with pseudostem — Correct

• Ginger has a pseudostem made from leaf bases.

✅ III. Malabar spinach : Herbaceous climber — Correct

• It is a soft-stemmed climbing herb.

❌ IV. Mint : Annual shrub — Incorrect

• Mint is a perennial herb, not a shrub.

❌ V. Papaya : Woody shrub — Incorrect

• Papaya is a large herbaceous plant, not woody.

So, the correct answer is: B (Only three)

Explanation

Direct Air Capture (DAC) is a technology that removes CO₂ directly from the air for storage or use in various industries.

✅ Statement I is correct:

• DAC captures CO₂ for carbon sequestration, reducing greenhouse gases.

✅ Statement II is correct:

• Captured CO₂ can be used to make plastics and in food processing.

✅ Statement III is correct:

• DAC provides carbon to make synthetic low-carbon aviation fuels by combining with hydrogen.

So, the correct answer is: C