UPSC Prelims 2015— Question 93

Correct answer: Option D. Railway bio-toilets use bacterial or microbial processes to decompose human waste in an anaerobic environment. The decomposition does not begin through a fungal inoculum, and the products are not limited to ammonia and water vapour. Therefore neither statement correctly describes the process as framed in the question. Option-wise analysis: Option A: “1 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: “Both 1 and 2” 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 D: “Neither 1 nor 2” is correct. It directly matches the factual or conceptual requirement tested by the question and is supported by the principle explained above. 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.