The pollutants which come directly in the air from sources are called primary pollutes. Primary polluants are sometimes converted into secondary pollutants. Which of the following belongs to secondary air pollutants ?

Options

A. CO
B. Hydrocarbon
C. Peroxyacetyl nitrate
D. NO

Explanation

To determine which of the given options belongs to secondary air pollutants, we need to understand the difference between 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 factories, vehicles, and burning fossil fuels. Examples include sulfur dioxide (SO2), nitrogen oxides (NOx), carbon monoxide (CO), and particulate matter.

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

3. **Identify Examples of Secondary Pollutants**:
- Common examples of secondary pollutants include:
- Ozone (O3) at ground level, which forms from the reaction of sunlight with primary pollutants like nitrogen oxides and volatile organic compounds.
- Smog, which is a mixture of fog and smoke, often formed from the reaction of sunlight with pollutants.
- Peroxyacetyl nitrate (PAN), which is formed from the reaction of nitrogen oxides and volatile organic compounds.

4. **Evaluate the Options**:
- Based on the definitions and examples provided, we need to look at the options given in the question. Among the options, we need to identify which one is formed from the reactions of primary pollutants.

5. **Select the Correct Answer**:
- If one of the options is peroxyacetyl nitrate (PAN), then that is the correct answer, as it is a secondary pollutant formed from the reactions of primary pollutants.

### Conclusion:
- The correct answer to the question is **peroxyacetyl nitrate (PAN)**, as it is a secondary air pollutant formed from the reactions of primary pollutants.