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.  

on the planet jupiter, the acceleration due to gravity is approximately 26 m s2 , roughly 2.7 times the acceleration due

answer: the correct option is d. enzyme

lactase and carbonic anhydrase are the examples of enzymes.

lactase is an enzyme, which is present in the small intestine of mammals. it in the digestion of the disaccharide, lactose ( milk sugar) by converting it into two monosachharide, which are glucose and galactose.

carbonic anhydrase is present in the red blood cells. this enzyme plays significant role in the transport of co₂. it in the conversion of co₂ and h₂o into carbonic acid, which is then dissociated into bicarbonate ions and hydrogen ions.