Which of the following act as secondary pollutants ?

Options

A. `CO_(2)`
B. `SO_(3)`
C. `NO_(2)`
D. `O_(3)`

Answer

To determine which of the following acts as secondary pollutants, we first need to understand the distinction between primary and secondary pollutants.

### Step-by-Step Solution:

1. **Definition of Pollutants**:
- **Primary Pollutants**: These are pollutants that are emitted directly from a source into the atmosphere. Examples include carbon dioxide (CO2), carbon monoxide (CO), sulfur dioxide (SO2), nitrogen oxides (NO, NO2), etc.
- **Secondary Pollutants**: These are not emitted directly. Instead, they form in the atmosphere through chemical reactions between primary pollutants and other atmospheric constituents.

2. **Examples of Secondary Pollutants**:
- Common examples of secondary pollutants include ozone (O3), sulfur trioxide (SO3), and nitrogen pentoxide (N2O5).
- For instance, sulfur trioxide (SO3) can react with water vapor in the atmosphere to form sulfuric acid (H2SO4), which is a component of acid rain.

3. **Identifying Secondary Pollutants**:
- To identify secondary pollutants from a list, look for substances that are formed through reactions involving primary pollutants or other environmental components.
- For example, if ozone (O3) is listed, it is a secondary pollutant because it forms from the reaction of sunlight with primary pollutants like nitrogen oxides (NOx) and volatile organic compounds (VOCs).

4. **Conclusion**:
- Based on the definitions and examples, we can conclude that substances like O3, SO3, and N2O5 are secondary pollutants, while CO2, CO, SO2, NO, and NO2 are primary pollutants.

### Final Answer:
The secondary pollutants from the options provided are O3 (ozone), SO3 (sulfur trioxide), and N2O5 (nitrogen pentoxide).

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