The stoma on the underside of the leaf will when the turgor pressure within the guard cells increases to full capacity

A. Swell
B. Shrink
C. Open fully
D. Close tightly

A.

Explanation:

When animals eat their food combine with oxygen, which produces energy for the animals to use for everyday activity and then gives off carbon. The carbon then combines with the oxygen to form carbon dioxide, which is then released back into the atmosphere as waste product when the animals breath.

Carbon Dioxide (CO2)

Hope this helps ;)