Which geomorphic clue indicates that the Aravalli Range is ancient?

Correct answer: Low height and intense erosion

Direct answer: Option A, low height and intense erosion. A very old mountain range has been exposed to weathering and erosion for a long geological period. Erosion wears down slopes and peaks, so an ancient range generally has lower, more rounded, and less rugged relief than a young, actively rising range. The Aravalli Range is among India’s oldest fold mountain systems and has been greatly denuded. Option A is therefore the correct geomorphic clue. Option B is wrong because permanent glaciers require sufficiently high, cold peaks and do not by themselves indicate that a range is ancient. Option C is wrong because a tidal delta forms from sediment deposition at a coast, not from mountain age. Option D is wrong because a marine coral ring is a reef feature, unrelated to an eroded mountain range. Memory cue: old mountains are worn down; young mountains are usually higher and sharper.