Below given are two statements, one is labelled as Assertion (A) and the other as Reason (R). Assertion (A): The rivers of the West Coast of India do not form the delta. Reason (R): They flow through short courses on relatively harder rocks. Select the correct answer from the codes given below:

Both the assertion and the reason are true, and the reason explains the assertion. Most west coast rivers, such as the Mandovi, Zuari, Sharavati and Periyar, are short, steep and swift because they rise close to the Western Ghats and reach the Arabian Sea quickly. Their catchments are small, and they flow over hard crystalline and Deccan trap rocks that yield little sediment. With so little alluvium reaching the mouth, no delta builds up. Instead the rivers form estuaries and creeks, which are drowned river mouths.

• Option B is wrong because the short course and limited sediment supply are exactly why no delta forms, so the reason explains the assertion.
• Option C is wrong because the reason is true: the short courses over hard rocks are the standard explanation.
• Option D is wrong because the assertion is correct.

This links to coastal geomorphology in Physical Geography and to Mains questions on estuarine ports such as Mumbai and Kochi.

Trap: Candidates pick B because they know the rivers are short but do not see the causal link to sediment supply and the absence of a delta.