The correct option is (a).
Explanation
Drainage describes the flow of water through well-defined channels. The specific terminology used in physical geography distinguishes between the network of channels, the area they drain, and the physical boundaries separating them.Statement-wise Analysis:
- Statement 1 is Correct: The area drained by a single river system (comprising the main river and its tributaries) is technically called a drainage basin. It represents the entire geographical area from which the river system collects water.
- Statement 2 is Incorrect: An elevated area, such as a mountain, hill, or upland, that separates two adjacent drainage basins is known as a water divide (or watershed divide). A "river system" refers to the river along with its tributaries, not the separating landform. For example, the Ambala water divide separates the Indus and Ganga drainage systems.
- Statement 3 is Incorrect: The world’s largest drainage basin belongs to the Amazon River in South America. While the Nile River in Africa is the longest river in the world, its drainage basin area is smaller than that of the Amazon.
Key Takeaway: A drainage basin is the total area drained by a river system, whereas a water divide is the elevated boundary separating two basins. The Amazon holds the record for the largest drainage basin, while the Nile is the longest river.