Examples of secondary air pollutants is/are:

Options

A. Automobile exhausts
B. chimneys smog
C. photochemicals smog
D. Classical smog

Answer

To solve the question regarding examples of secondary air pollutants, we will analyze the given options step by step.

### Step 1: Understand the Definitions
- **Primary Pollutants**: These are pollutants that are directly emitted from a source. Examples include carbon monoxide, sulfur dioxide, and nitrogen oxides.
- **Secondary Pollutants**: These are not emitted directly but are formed through chemical reactions between primary pollutants and other atmospheric components.

### Step 2: Analyze the Options
1. **Automobile Exhaust**: This is a mixture of gases emitted from vehicles, which includes primary pollutants like carbon monoxide and nitrogen oxides. Therefore, it is not a secondary pollutant.

2. **Chimney Smog**: Similar to automobile exhaust, chimney smog contains primary pollutants from burning fuels. Thus, it is also not a secondary pollutant.

3. **Photochemical Smog**: This is formed when sunlight reacts with primary pollutants such as nitrogen oxides and volatile organic compounds (unsaturated hydrocarbons). The reaction produces secondary pollutants like ozone and peroxyacetyl nitrate. Hence, photochemical smog is a secondary pollutant.

4. **Classical Smog**: This type of smog is formed from the combination of smoke and fog, primarily consisting of sulfur dioxide, which is a primary pollutant. Therefore, classical smog is not a secondary pollutant.

### Step 3: Conclusion
Based on the analysis, the correct answer to the question is **Photochemical Smog**, which is an example of a secondary air pollutant.

### Final Answer
The example of a secondary air pollutant is **Photochemical Smog**.

---