In the carbon cycle, all animals must consume other organisms because
A. they can not absorb enough carbon from water.
B. they cannot absorb carbon directly from the air.
C. they are in competition with plants for available
carbon.
D. they require carbon to perform photosynthesis.

B is the anwser, I think.

Explanation:

1.  animals cannot perform photosynthesis

2. animals cannot go into competion with plants because plants are in a total different kingdom

3. Carbon is not in water,  yes there might be a charcol-carbon water filter, yet  carbon isn't in water

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.