UPSC Prelims 2021— Question 23

ACE2 is angiotensin-converting enzyme 2, a host-cell receptor involved in the entry of SARS-CoV-2 and therefore widely discussed during the COVID-19 pandemic. It is a biological receptor and not a gene introduced into crops, a satellite-navigation component or a wildlife-tracking radio collar. The question links ACE2 to the spread and mechanism of viral disease. The final answer-key position for Set C identifies option D as the correct option. Option A — genes introduced in the genetically modified plants — 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 — development of India’s own satellite navigation system — 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 C — radio collars for wildlife tracking — 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 — spread of viral diseases — is correct because it is the alternative that matches the constitutional, historical, geographical, scientific or economic principle established above. 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.