which of the following secondary pollutants ? (a) `CO_2` (b) ozone (c) PAN (d) CO

Options

A. (a) & (b)
B. (b) & (c)
C. (c) &(d)
D. (a) &(d)

Answer

To determine which of the given options are secondary 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 emitted directly into the atmosphere from sources such as vehicles, factories, 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 atmospheric components.

3. **Analyze Each Option**:
- **(a) CO2 (Carbon Dioxide)**: This is a primary pollutant as it is released directly from sources like respiration, combustion of fossil fuels, and deforestation.
- **(b) Ozone (O3)**: Ozone is considered a secondary pollutant because it forms when primary pollutants like volatile organic compounds (VOCs) and nitrogen oxides (NOx) react in the presence of sunlight.
- **(c) PAN (Peroxyacetyl Nitrate)**: PAN is also a secondary pollutant. It is formed from the reaction of carbon monoxide and nitrogen oxides in the atmosphere.
- **(d) CO (Carbon Monoxide)**: This is a primary pollutant as it is emitted directly from sources such as vehicle exhaust and industrial processes.

4. **Conclusion**:
- From the analysis, the secondary pollutants among the options are **(b) Ozone** and **(c) PAN**. Therefore, the correct answer is **B and C**.

### Final Answer:
The secondary pollutants from the given options are **(b) Ozone** and **(c) PAN**.

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