The steep gradient of the river have more or less energy of river?

The total energy that a river possesses varies from one stage to another because of changes in the river's height, gradient and speed. In the upper course where the gradient is steep and river is high above sea level,  the river has a high gravitational  potential energy.  In the middle course, the potential gravitational energy is converted to kinetic energy and the gradient begins to level out resulting in the river's velocity increasing.

By the time the river reaches its lower stage, it has no gravitational potential energy but lots of kinetic energy resulting in a high velocity. 

the answer is:

c. islam and christianity

explanation:

islam and christianity are widely practiced in africa. islam is practiced due to its spread from the middle east into africa, and christianity is practiced due to the colonization of africa by the british empire.