Which is not an air pollutant?

Options

A. `H_(2)`
B. `H_(2)S`
C. `SO_(2)`
D. `O_(3)`

Answer

To determine which of the given options is not an air pollutant, we will analyze each option one by one.

### Step-by-Step Solution:

1. **Identify the Options**: The options given are:
- A) H2 (Hydrogen gas)
- B) H2S (Hydrogen sulfide)
- C) SO2 (Sulfur dioxide)
- D) O3 (Ozone)

2. **Analyze Option A: H2 (Hydrogen gas)**:
- Hydrogen gas is a clean fuel that does not produce harmful emissions when burned. It is considered environmentally friendly and does not contribute to air pollution. Therefore, H2 is **not an air pollutant**.

3. **Analyze Option B: H2S (Hydrogen sulfide)**:
- Hydrogen sulfide is a toxic gas that can be harmful to both humans and the environment. It can cause damage to aquatic life and is considered an air pollutant. Thus, H2S is an **air pollutant**.

4. **Analyze Option C: SO2 (Sulfur dioxide)**:
- Sulfur dioxide is known to contribute to air pollution and is a precursor to acid rain. It can cause respiratory problems and environmental damage. Therefore, SO2 is also an **air pollutant**.

5. **Analyze Option D: O3 (Ozone)**:
- Ozone at ground level is considered an air pollutant as it can harm vegetation and human health. While ozone in the stratosphere protects us from UV radiation, ground-level ozone is detrimental to the environment. Thus, O3 is an **air pollutant**.

6. **Conclusion**:
- After analyzing all options, we find that:
- H2 is not an air pollutant.
- H2S, SO2, and O3 are all air pollutants.
- Therefore, the correct answer is **Option A: H2**.

### Final Answer:
**Option A: H2 (Hydrogen gas) is not an air pollutant.**