Which of the following gas in the atmosphere is not considered as a pollutant ?

Options

A. Hydrocarbons
B. Carbon dioxide
C. Carbon monoxide
D. Sulphur dioxide

Answer

To solve the question of which gas in the atmosphere is not considered a pollutant, we will analyze each option provided:

1. **Hydrocarbon**: Hydrocarbons are organic compounds made up of hydrogen and carbon. They are significant air pollutants primarily released from vehicle emissions and industrial processes. Therefore, hydrocarbons are considered pollutants.

2. **Carbon Dioxide (CO₂)**: Carbon dioxide is a naturally occurring gas that is produced during respiration by animals and plants. It is also released during combustion processes. Importantly, plants utilize carbon dioxide during photosynthesis to produce oxygen and glucose. Because of its essential role in the ecosystem and its natural occurrence, carbon dioxide is not classified as a pollutant.

3. **Carbon Monoxide (CO)**: Carbon monoxide is a colorless, odorless gas that is produced from incomplete combustion of fossil fuels. It is toxic and can lead to serious health issues, making it a significant air pollutant.

4. **Sulfur Dioxide (SO₂)**: Sulfur dioxide is produced from volcanic eruptions and industrial processes, particularly the burning of fossil fuels containing sulfur. It can cause respiratory problems and environmental issues like acid rain, thus it is also considered a pollutant.

Based on this analysis, the gas that is not considered a pollutant is **Carbon Dioxide (CO₂)**.

### Final Answer:
**Carbon Dioxide (CO₂)** is not considered a pollutant.