Which one of these is NOT an air pollutant?

Options

A. Carbon monoxide
B. Sulphur dioxide
C. Oxygen
D. Lead

Explanation

To determine which of the given options is NOT an air pollutant, we can analyze each option step by step.

### Step-by-Step Solution:

1. **Identify the Options**: The options provided are:
- A) Carbon Monoxide
- B) Sulphur Dioxide
- C) Oxygen
- D) Lead

2. **Analyze Carbon Monoxide**:
- Carbon Monoxide (CO) is a gas that can bind with hemoglobin in the blood, forming carboxyhemoglobin. This reduces the blood's ability to carry oxygen, leading to health issues. Therefore, carbon monoxide is an air pollutant.

3. **Analyze Sulphur Dioxide**:
- Sulphur Dioxide (SO2) is produced from the combustion of fossil fuels and can cause respiratory problems, skin issues, and contribute to acid rain. Thus, sulphur dioxide is also an air pollutant.

4. **Analyze Oxygen**:
- Oxygen (O2) is essential for life and is required for respiration in most living organisms. It is not harmful and is a natural component of the air we breathe. Therefore, oxygen is NOT an air pollutant.

5. **Analyze Lead**:
- Lead is often released into the air from leaded petrol during combustion. It can cause serious health issues, including brain damage and anemia. Hence, lead is also considered an air pollutant.

6. **Conclusion**:
- After analyzing all the options, we find that the only substance that is NOT an air pollutant is **Oxygen**.

### Final Answer:
**C) Oxygen**

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