Maya wrote a few steps to describe how carbon circulates between the atmosphere and living organisms. step 4 is missing.
step 1: carbon enters the atmosphere as carbon dioxide from respiration and combustion
step 2: plants use carbon dioxide to make glucose
step 3: plant-eating animals consume the glucose present in plants
step 4:
which of the following best describes step 4?

The glucose is broken down in the blood to release CO2 ,which returned to the atmosphere through the process of respiration  !

Explanation:

When the animal eats the plant , the glucose is absorbed in the blood stream through the intestine.The glucose enter the cell,through the cytoplasm into the mitrochondria Mitrochondria is called the power house of the cell , it generates the energy through break down of glucose The process of breaking the glucose into energy is a cycle called the glycolysis .At the end of this process CO2 is by product ,that is taken by circulating blood to the lungs From there through the alveoli the gases are exchange due to difference in the partial pressure and CO2 is expelled out and oxygen enters blood stream and the cycle continues .

  like australopithecus afarensis; probably the direct ancestor of this group. africa: 5.8 to 4.4 million years ago.