UPSC Prelims 2021— Question 72

Cyanobacteria and diatoms are photosynthetic organisms and important primary producers in marine food webs. Copepods and foraminifera are generally consumers rather than primary producers, although some foraminiferal species have photosynthetic symbionts. The basic food-chain classification asked by the question therefore identifies statements 2 and 3. The final answer-key position for Set C identifies option B as the correct option. Option A — 1 and 2 — is not correct because it does not satisfy the specific condition tested in the question; it represents an alternative that is contradicted, incomplete, or less precise than the accepted answer. Option B — 2 and 3 — is correct because it is the alternative that matches the constitutional, historical, geographical, scientific or economic principle established above. Option C — 3 and 4 — is not correct because it does not satisfy the specific condition tested in the question; it represents an alternative that is contradicted, incomplete, or less precise than the accepted answer. Option D — 1 and 4 — is not correct because it does not satisfy the specific condition tested in the question; it represents an alternative that is contradicted, incomplete, or less precise than the accepted answer. For PYQ interpretation, the distinction between the correct alternative and merely related facts is important. UPSC often places plausible distractors beside the precise statement that matches the underlying rule, chronology, definition or empirical relationship. The answer should therefore be read against the exact wording of the question rather than against a broadly related fact.