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 substances act as secondary pollutants, we need to first 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), sulfur dioxide (SO₂), and nitrogen oxides (NOx).

2. **Define Secondary Pollutants:**
- Secondary pollutants are not emitted directly. Instead, they form in the atmosphere through chemical reactions involving primary pollutants. These reactions often require sunlight or other environmental conditions.

3. **Identify Examples of Secondary Pollutants:**
- Common examples of secondary pollutants include:
- **Ozone (O₃):** Formed when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react in the presence of sunlight.
- **Acid Rain:** Formed when sulfur dioxide (SO₂) and nitrogen oxides (NOx) react with water vapor in the atmosphere.
- **Peroxyacetyl Nitrate (PAN):** Formed from reactions involving hydrocarbons and nitrogen oxides.

4. **Analyze the Given Options:**
- Review the list of substances provided in the question to identify which ones are formed through reactions of primary pollutants.
- For example, if the options include ozone, sulfur dioxide, and carbon dioxide:
- **Ozone** is a secondary pollutant.
- **Sulfur Dioxide** is a primary pollutant.
- **Carbon Dioxide** is generally not classified as a pollutant in this context.

5. **Conclude:**
- Based on the definitions and examples, select the substances that qualify as secondary pollutants from the provided options.