Correct Option: A

The course of a river from its source to its mouth is normally divided into 3 sections, namely upper, middle and lower courses. Action of the river on its valley from source to mouth in relation to the features developed by it is seen in he river valley profile, known as graded profile. Throughout the long profile of a river, deposition and erosion are balanced meaning that, given enough time, the river’s long profile would become a smooth, concave, graded profile from its source to mouth.