Which characteristic describes a mature river?

a. has a steep stream gradient

b. has many tributaries

c. is near headwaters

d. is in a straight and narrow v-shaped channel

B. Has many tributaries

A river is a water body which in which water is originated from different sources like like lake, melting glaciers, rainwater, groundwater. All rivers join to these sources of water and these sources are called as tributaries which combine to form headwater. A young river will have few tributaries that is it will originate from few water sources but a mature river will have many tributaries.  

answer; the above statement is (true);