I'm pretty sure it is "c"
Answer:
River basin is the area of land that is drained by a river system.
Explanation: River basin is also called drainage basin. River basin consist of one main big stream which collects water from many tributaries present on the left and right of the main stream. Water is collected from high ridge areas into these tributaries due to precipitation over there. These high areas is known as watershed. This main stream flows and drain into a river system.