The role of a watershed is to
a. purify water.
b. act as a drainage area.
c. collect fish from rivers and streams.
d. protect wetland areas.

The right answer is B. act as a drainage area.

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.