Answer:
D. Niger River
Step-by-step explanation:
The most important source of fresh water in the western Sahel region is the "Niger River".
The Niger River is known to be the third largest river after the Nile and the Congo. It is the principal river of western Africa. It has a length of 2,600 miles (4,200 km). Niger River is known to be a typical Sahelian river. It has distinct wet and dry seasons. It's an important source of fresh water to Western Sahel.
The Sahel region is known to be a 3,860-kilometre arc-like land mass.
It lies in the south of the Sahara Desert and stretches east-west across the breadth of the African continent