Plants provide humans with CO_2 for respiration. Animals release CO_2, required for photosynthesis. Plants provide humans with atmospheric nitrogen. Animals release O_2, required for plant survival.
I gave my students this multiple choice question: Which statement accurately describes an interaction between plants and animals?

Only one answer is correct among these 4 choices:
- Plants provide humans with CO_2 for respiration.
- Animals release CO_2, required for photosynthesis.
- Plants provide humans with atmospheric nitrogen.
- Animals release O_2, required for plant survival.

Could you tell me which one is correct?

Animals release CO_2, required for photosynthesis.