The area drained by a single river system is called ______.
A- Water divide
B- Drainage basin
C- River system
D- Perennial river
E- None of these

Hint:
It is also known as a watershed. Some other names for it are Catchment area, catchment basin, drainage area, river basin, a water basin, and impluvium are other terms for a drainage basin.

Complete answer:
The drainage basin is called the region drained by a single river system. Sometimes with drainage basin or catchment, the word watershed is used interchangeably.

It represents all of the tributaries of the stream that flow along the stream channel to some location. The number, size and shape of drainage basins discovered in an area varies with the examination scale. Based on the topographic information accessible on a map, drainage basins are arbitrarily specified.

A drainage basin provides a restricted surface area within which it is possible to consider physical processes relevant to general hydrology. The climatic variables and the discharge of water and sediment, water accumulation and evapotranspiration can be measured; denudation rates and moisture and energy balances can be extracted from these measurements, each of which is useful for considering and understanding landscape formation.

Therefore, the correct answer is B

Note:
Water Divide-The water divide is known as an elevated area, such as a mountain or an upland that separates two drainage basins.

River System-A river system is a number of rivers consisting of a single main river that drains and all its tributaries into a lake or into the ocean.

Perennial river- A perennial stream or perennial river is a stream or river (channel) that has a continuous stream throughout years of regular rainfall during the year across parts of its stream bed.