UPSC Prelims 2025— Question 28

This question tests the UPSC concept of Permeability and Chalk within Geomorphology. The correct answer is option C, which corresponds to “Only one of II and III is correct and explains I”. The key point is to read each statement or alternative literally and distinguish the constitutional, institutional, scientific, geographical or economic rule being tested from plausible-sounding distractors. Option A — “Both II and III correct and both explain I” — is assessed against the underlying concept; it is correct only when it satisfies the condition stated in the question. Option B — “Both II and III correct but only one explains I” — is similarly tested against the same rule rather than against a superficial association. Option C — “Only one of II and III is correct and explains I” — can be attractive because it often combines statements that are individually familiar, but a single incorrect statement makes a combination option incorrect. Option D — “Neither II nor III is correct” — must also be checked independently; UPSC frequently uses an absolute word, an incorrect institutional attribution, an incorrect chronology, or an over-broad statement as the elimination point. For this PYQ, the decisive reasoning is therefore the distinction captured by the keyed option C. The question should be approached by first identifying the subject domain, then verifying each statement separately, and finally mapping the valid statements to the answer code. This also illustrates an important Prelims technique: do not select an option merely because one statement is unquestionably correct. Where the question asks how many statements are correct or which combination is correct, every component has to survive verification. The distractors are useful for revision because they identify the nearby concepts that can be confused with the tested one. In practice, an aspirant should retain the underlying principle rather than memorise the option letter. The final answer in this database follows the consolidated Set-A answer-key reference used for verification, while the question wording and options are based on the uploaded UPSC paper scan.