A secondary polluntants is

Options

A. CO
B. `CO_(2)`
C. PAN
D. Aerosol

Answer

To determine which of the given options is a secondary pollutant, we need to understand the definitions and characteristics of primary and secondary pollutants.

### Step-by-Step Solution:

1. **Define Primary Pollutants**: Primary pollutants are substances that are directly emitted into the atmosphere from sources such as vehicles, industries, and natural events. Examples include carbon monoxide (CO) and carbon dioxide (CO2).

2. **Define Secondary Pollutants**: Secondary pollutants are not emitted directly. Instead, they form in the atmosphere through chemical reactions between primary pollutants and other substances.

3. **Analyze the Options**:
- **Option A: Carbon Monoxide (CO)**: This is a primary pollutant produced from incomplete combustion of fossil fuels.
- **Option B: Carbon Dioxide (CO2)**: This is also a primary pollutant, primarily released from burning fossil fuels and biomass.
- **Option C: PAN (Peroxyacetyl Nitrate)**: This is a secondary pollutant formed from the reaction of hydrocarbons (which are primary pollutants) with oxygen in the presence of sunlight.
- **Option D: Aerosol**: Aerosols can be both primary and secondary pollutants, but in this context, they are considered primary.

4. **Identify the Correct Answer**: Since PAN is formed through reactions involving primary pollutants, it qualifies as a secondary pollutant. Therefore, the correct answer is **Option C: PAN**.

### Final Answer:
A secondary pollutant is **PAN (Peroxyacetyl Nitrate)**, which is formed by the reaction of hydrocarbons with oxygen.

---