Photochemical smog is characterized by the absence of

Options

A. Ozone
B. nitrogen dioxide
C. Carbon dioxide
D. PAN

Answer

To solve the question regarding what photochemical smog is characterized by the absence of, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Photochemical Smog**:
- Photochemical smog is a type of air pollution that occurs when sunlight reacts with pollutants such as volatile organic compounds (VOCs) and nitrogen oxides (NOx) in the atmosphere.

2. **Identifying Components of Photochemical Smog**:
- The main components of photochemical smog include:
- Ozone (O3)
- Nitrogen Dioxide (NO2)
- Peroxyacetyl Nitrate (PAN)

3. **Analyzing the Options**:
- The question asks what is absent in photochemical smog. The options typically include various gases.
- From our understanding, we know that ozone, nitrogen dioxide, and PAN are present in photochemical smog.

4. **Identifying the Correct Answer**:
- Since carbon dioxide (CO2) is not a component of photochemical smog, we can conclude that the correct answer is carbon dioxide.

5. **Final Answer**:
- Photochemical smog is characterized by the absence of carbon dioxide.