Question

how does carbon get from animals and back into the atmosphere? (choose all that apply)
respiration (breathing)
photosynthesis
after they die, they are broken down by decomposers
none of these

Explanation:

1. Respiration (breathing): Animals perform cellular respiration, which releases carbon dioxide ($\ce{CO_2}$) into the atmosphere. This is a key way carbon from animals returns to the atmosphere.
2. After they die, they are broken down by decomposers: When animals die, decomposers (like bacteria and fungi) break down their organic matter. This decomposition process releases carbon - containing compounds, including $\ce{CO_2}$, back into the atmosphere.
3. Photosynthesis: This is a process carried out by plants, algae, and some bacteria. It uses carbon dioxide from the atmosphere to make glucose. So it is a process that removes carbon from the atmosphere (for use in building plant matter), not a way for carbon from animals to get back into the atmosphere.
4. None of these: Since Respiration and decomposition by decomposers are valid ways for carbon from animals to return to the atmosphere, this option is incorrect.

Answer:

A. Respiration (breathing), C. After they die, they are broken down by decomposers