The correct answer is B. acts as an drainage area.
A watershed is surface area on land where all the rain water collected and drained through a common point into a water bodies such as river, lake or stream. A watershed is also called a drainage basin or catchment area. Watersheds conserve water and make river, streams flow uninterrupted. It recharges ground water and provide dwelling place for wildlife and plants.
A watershed or watershed is the space drained by a watercourse and its tributaries. All the waters that fall into this space converge towards the same exit point called an outlet: stream, lake, sea, ocean, etc.
The watershed is bounded by a watershed that often corresponds to the ridge lines but not always. Generally a watershed develops beyond the ridge lines. A watershed is a divergent line of slopes. Rainwater on both sides of this line flows in two different directions, carrying with them dissolved or suspended elements such as sediments and pollution.