नदीय भू-आकृति विज्ञान के संदर्भ में, निम्नलिखित में से कौन 'सरिता सामर्थ्य' (Stream Competence) को सबसे अच्छी तरह परिभाषित करता है?

Given below are two statements, one labelled as Assertion (A) and the other as Reason (R): Assertion (A): The valley sides and valley floors of rivers are vigorously eroded through abrasion in hilly regions. Reason (R): A steep channel gradient accelerates the abrasive power and erosive capacity of rivers. Select the correct answer:

Consider the following Assertion (A) and Reason (R): Assertion (A): Impoundment of a river by a dam decreases its downstream sediment entrainment capacity. Reason (R): Water velocity drops inside a reservoir, causing sediment deposition before water is released downstream. Select the correct option: