Respiration and photosynthesis both add carbon to the atmosphere. Respiration and photosynthesis both remove carbon from the atmosphere. Respiration adds carbon to the atmosphere, while photosynthesis removes carbon from the atmosphere. Photosynthesis adds carbon to the atmosphere, while respiration removes carbon from the atmosphere.
I gave my students this multiple choice question: Which statement best describes the roles of photosynthesis and respiration in the carbon cycle?

Only one answer is correct among these 4 choices:
- Respiration and photosynthesis both add carbon to the atmosphere.
- Respiration and photosynthesis both remove carbon from the atmosphere.
- Respiration adds carbon to the atmosphere, while photosynthesis removes carbon from the atmosphere.
- Photosynthesis adds carbon to the atmosphere, while respiration removes carbon from the atmosphere.

Could you tell me which one is correct?

Respiration adds carbon to the atmosphere, while photosynthesis removes carbon from the atmosphere.