Which gas in the atmosphere is utilised by the trees and plants in photosynthesis ?

Explanation

### Step-by-Step Solution:

1. **Identify the Process**: The question asks about the gas utilized by trees and plants during photosynthesis. Photosynthesis is the process through which plants convert light energy into chemical energy.

2. **Recognize the Key Components**: In photosynthesis, plants require certain components to produce food. The main components involved are sunlight, water, and gases from the atmosphere.

3. **Focus on the Gas**: Among the gases present in the atmosphere, one specific gas is crucial for photosynthesis. This gas is absorbed by plants through small openings in their leaves called stomata.

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