What is the correct meaning of a river basin?

Correct answer: Area drained by a river and its tributaries

The direct answer is option B. A river basin is the complete area from which rainwater and other surface water drain into one main river and its tributaries. To identify it, trace the streams joining the river and imagine the high land or watershed boundary around them. Option A is wrong because a delta is only the depositional mouth region of a river, not the whole drainage area. Option B is correct because it describes the entire area served by a river system. Option C is wrong because a basin is not defined as a plain below sea level. Option D is wrong because the deepest channel is only one part of a river, not the land that supplies water to it. Memory cue: basin means the bowl-like drainage area, while tributaries are smaller streams joining the main river.