Which gas is removed from the atmosphere during photosynthesis?

1. Oxygen (O₂)
2. Carbon dioxide (CO₂)
3. Nitrogen (N₂)
4. None of the above

Answer: (2) Carbon dioxide (CO₂)

Explanation

Plants take in CO₂ from the atmosphere and use it to build organic molecules during photosynthesis, effectively removing it from the air. While oxygen is produced as a byproduct, it wasn’t initially present in the atmosphere.