Given below are two statements, one is labelled as Assertion (A) and other as Reason (R): Assertion (A): Teesta river was earlier a tributary of Ganga now it is a tributary of Brahmaputra. Reason (R) : River capturing is a major feature of Himalayan rivers. Select the correct answer using the codes given below. Codes :

Both statements are true, but the reason only describes a general feature and does not directly explain the specific shift in the Teesta.

Assertion (A) is true. The Teesta originally drained into the Ganga system through the Atrai and Punarbhaba channels. Over time it shifted its course and now joins the Brahmaputra. This is a classic example of river capture, where a stronger river diverts the flow of a neighbouring one.

Reason (R) is true. River capture is indeed common in the Himalayan region, because steep gradients, rapid headward erosion and young, unstable drainage make diversion frequent. Examples include the Kosi's westward shifts and the Sutlej-Beas and Teesta cases.

Why R is not the explanation. R states a general geomorphic tendency. It does not specifically account for why the Teesta changed its course. The specific mechanism, capture by a Brahmaputra-side channel, is a particular case of that tendency, so R is related but not the explanation the assertion needs.

Mains angle: the Teesta shift is a useful case study for flood management, river-linking debates and Sikkim-Bengal water disputes.

Trap: candidates see that both statements are true and pick A, assuming R explains A. Ask whether R gives the specific reason for the event, not just a related general feature.