I believe the answer is "A". Please correct me.

Which statement best describes the role of animals in the water and carbon cycles?

Select one:
a. Animals release carbon dioxide and water vapor as a by‐product of cellular respiration.
b. Animals release carbon dioxide and water vapor as a by‐product of photosynthesis.
c. Animals take in carbon dioxide and oxygen during cellular respiration.
d. Animals use oxygen to perform photosynthesis and release carbon dioxide as a by‐product.