04-a watershed is:
a. the area drained by a sewer system
b. the area contributing water to the runoff of a stream system
c. the area covered by the groundwater table
d. the area between two mountains

The correct answer is B. A watershed is the area contributing water to the runoff of a stream system.

Explanation:

A watershed or hydrographic basin is a territory drained by a single natural drainage system, that is, its waters give the sea through a single river or that it pours its waters to a single endorheic lake. A hydrographic basin is delimited by the line of the summits, also called water division. The use of natural resources is regulated administratively by separating the territory by river basins, and with a view to the future the river basins are emerging as one of the functional division units with much more coherence, allowing true social and territorial integration through water.