Air pollutant photochemical oxidants include
(a) nitrous oxide, nitric acid and nitric oxide
(b) oxygen, chlorine and nitric acid
(c) ozone, peroxyacetyl nitrate and aldehydes
(d) carbon monoxide and sulphur dioxide

Options

A. nitrous oxide, nitric acid and nitric oxide
B. oxygen, chlorine and nitric acid
C. ozone, peroxyacetyle nitrate and aldehydes
D. carbon monoxide and sulphur dioxide.

Answer

To solve the question regarding which compounds are classified as air pollutant photochemical oxidants, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Photochemical Oxidants**:
- Photochemical oxidants are secondary pollutants formed when primary pollutants react with sunlight. They are not directly emitted but are produced through chemical reactions in the atmosphere.

2. **Identify Primary Pollutants**:
- Common primary pollutants include hydrocarbons, nitrogen oxides (NOx), and sulfur oxides (SOx). These pollutants undergo reactions in the presence of sunlight to form secondary pollutants.

3. **Review the Options**:
- (a) Nitrous oxide, nitric acid, and nitric oxide
- (b) Oxygen, chlorine, and nitric acid
- (c) Ozone, peroxyacetyl nitrate, and aldehydes
- (d) Carbon monoxide and sulfur dioxide

4. **Analyze Each Option**:
- **Option (a)**: Nitrous oxide (N2O), nitric acid (HNO3), and nitric oxide (NO) are products of reactions involving primary pollutants and can contribute to photochemical smog. However, nitrous oxide is not typically classified as a photochemical oxidant.
- **Option (b)**: Oxygen and chlorine are not classified as photochemical oxidants, and nitric acid is a secondary pollutant but not a photochemical oxidant.
- **Option (c)**: Ozone (O3), peroxyacetyl nitrate (PAN), and aldehydes are well-known photochemical oxidants formed from reactions involving primary pollutants.
- **Option (d)**: Carbon monoxide (CO) and sulfur dioxide (SO2) are primary pollutants and do not fit the definition of photochemical oxidants.

5. **Select the Correct Answer**:
- Based on the analysis, **Option (c)**: Ozone, peroxyacetyl nitrate, and aldehydes are indeed classified as photochemical oxidants.

### Final Answer:
(c) ozone, peroxyacetyl nitrate, and aldehydes