Which of the following is pollutant as well as protectant?

Options

A. `CO_(2)`
B. Ozone
C. CFC
D. PAN

Explanation

**Step-by-Step Solution:**

1. **Understanding Pollutants and Protectants**:
- A pollutant is a substance that causes harm to the environment or living organisms. A protectant, on the other hand, is a substance that provides protection against harmful effects, such as UV radiation.

2. **Analyzing the Options**:
- **Carbon Dioxide (CO2)**: This is a byproduct of respiration and is not a protectant. It is considered a pollutant due to its role in global warming.
- **Ozone (O3)**: Ozone can be both a pollutant and a protectant. In the stratosphere, it protects us from harmful UV rays, while at ground level, it can cause respiratory issues and eye irritation.
- **CFCs (Chlorofluorocarbons)**: These are pollutants that contribute to ozone depletion but do not provide any protective benefits.
- **PAN (Peroxyacyl Nitrate)**: This is primarily a pollutant that causes respiratory issues and eye irritation, with no protective function.

3. **Identifying the Correct Answer**:
- Among the options, ozone is the only substance that serves as both a pollutant (at ground level) and a protectant (in the stratosphere).

4. **Conclusion**:
- Therefore, the correct answer is **Ozone (O3)**, as it acts as both a pollutant and a protectant.

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