Which of the following is not involved in the formation of photochemical smog ?

Options

A. NO
B. `O_(3)`
C. `C_(x)H_(y)`
D. `SO_(2)`

Answer

To determine which of the following is not involved in the formation of photochemical smog, we need to understand the components that contribute to its formation.

### Step-by-Step Solution:

1. **Understand Photochemical Smog**: Photochemical smog is a type of air pollution that occurs when sunlight reacts with pollutants in the atmosphere. It is primarily composed of primary and secondary pollutants.

2. **Identify Primary Pollutants**: Primary pollutants are those that are directly emitted into the atmosphere. In the case of photochemical smog, the main primary pollutants include:
- Nitrogen oxides (NOx)
- Volatile organic compounds (VOCs)
- Unsaturated hydrocarbons (like ethylene, gasoline, and natural gas)

3. **Identify Secondary Pollutants**: Secondary pollutants are formed when primary pollutants react with other substances in the atmosphere. For example, sulfur dioxide (SO2) can be oxidized to sulfur trioxide (SO3) and can react with water to form sulfuric acid, which contributes to acid rain but is not a component of photochemical smog.

4. **Analyze the Options**: Given the components involved in photochemical smog, we need to evaluate the options provided in the question to identify which one is not a contributor to photochemical smog.

5. **Conclusion**: Based on the information, if one of the options is sulfur dioxide or sulfuric acid, it would be the correct answer as they are not involved in the formation of photochemical smog.

### Final Answer:
The component that is not involved in the formation of photochemical smog is **sulfur dioxide (SO2)** or **sulfuric acid (H2SO4)**, depending on the options given.

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