Photosynthesis is a process in which plants:

1. take in oxygen and give out carbon dioxide
2. take in carbon dioxide and give out oxygen
3. take in nitrogen and give out oxygen.
4. none of the above

take in carbon dioxide and give out oxygen

Reason — Photosynthesis is a process through which green plants prepare their food in presence of sunlight with the help of carbon dioxide and water. In this process carbon dioxide is consumed and oxygen is released.

Carbon dioxide + Water $\xrightarrow[\text{chlorophyll}]{\text{light}}$ Glucose + Oxygen