UPSC Prelims 2015— Question 11

Correct answer: Option C. Excessive nitrogen fertilizer can contribute to soil acidification through nitrification and related chemical processes. Nitrate is also highly mobile in water and can leach into groundwater, creating environmental and health concerns. The proliferation of nitrogen-fixing microorganisms is not the general consequence of simply adding nitrogen fertilizer; excess available nitrogen does not mean nitrogen fixation necessarily increases. Option-wise analysis: Option A: “1 and 3 only” is incorrect. It does not match the specific fact, definition, institutional role, geographical association, or constitutional/economic principle required here. The key distinction is the one identified in the core explanation, so this option can be eliminated. Option B: “2 only” is incorrect. It does not match the specific fact, definition, institutional role, geographical association, or constitutional/economic principle required here. The key distinction is the one identified in the core explanation, so this option can be eliminated. Option C: “2 and 3 only” is correct. It directly matches the factual or conceptual requirement tested by the question and is supported by the principle explained above. Option D: “1, 2 and 3” is incorrect. It does not match the specific fact, definition, institutional role, geographical association, or constitutional/economic principle required here. The key distinction is the one identified in the core explanation, so this option can be eliminated. Prelims takeaway: Focus on the precise institutional role, constitutional provision, geographical association, or technical definition being tested. UPSC questions often place a broadly familiar fact beside a narrowly incorrect qualifier; identifying that qualifier is essential for elimination.