UPSC Prelims 2023— Question 59

This question tests Mercury Pollution under Pollution & Toxicology. The central point is Gold mining and coal power are mercury sources and no safe exposure threshold is established. Option A: Only one. This distractor is not the keyed answer because it conflicts with the specific factual relationship, chronology, institutional role, geographic association or conceptual distinction tested in the question. Option B: Only two. This distractor is not the keyed answer because it conflicts with the specific factual relationship, chronology, institutional role, geographic association or conceptual distinction tested in the question. Option C: All three. This is the keyed answer because it matches the governing fact or concept: Gold mining and coal power are mercury sources and no safe exposure threshold is established. Option D: None. This distractor is not the keyed answer because it conflicts with the specific factual relationship, chronology, institutional role, geographic association or conceptual distinction tested in the question. The question should be approached by checking each statement independently rather than accepting a familiar phrase at face value. This is particularly important in UPSC questions where a single incorrect institutional attribution, location, chronology, absolute word or causal link can invalidate an otherwise plausible option. The broader revision takeaway is to connect the keyed answer with the underlying concept rather than memorizing only the letter. The options also illustrate how UPSC constructs distractors by mixing correct facts with one altered detail. In revision, candidates should therefore retain both the positive fact and the nearest contrasting fact so that the same concept can be recognized when the framing changes in another year.