The presence of gorges in the upper section of rivers is due to the fact that?

A.

The presence of gorges in the upper section of rivers is due to the fact that?

B.

the volume of the river is small

C.

hanging valleys join the main valley as waterfalls to cause the gorges

D.

the upper course has has a steep gradient

E.

the water contains chemicals which dissolve the rocks

Correct answer is D

No explanation has been provided for this answer.