Primary pollutants used in the synthesis of photochemical smog are -

Options

A. Unsaturated HCS
B. oxides of nitrogen
C. Ozone
D. Both a and b

Answer

To answer the question regarding the primary pollutants used in the synthesis of photochemical smog, we can follow these steps:

### Step 1: Understand Photochemical Smog
Photochemical smog is a type of air pollution that occurs when sunlight reacts with pollutants in the atmosphere. It is commonly seen in urban areas, especially during warm, sunny weather.

### Step 2: Identify Primary Pollutants
Primary pollutants are substances that are directly emitted into the atmosphere. In the case of photochemical smog, the key primary pollutants include:
- Unsaturated hydrocarbons (like ethene and benzene)
- Nitrogen dioxide (NO2)

### Step 3: Differentiate Between Primary and Secondary Pollutants
It is important to note that while ozone (O3) is a significant component of photochemical smog, it is classified as a secondary pollutant. This is because ozone is formed through reactions involving primary pollutants (like NO2 and hydrocarbons) in the presence of sunlight.

### Step 4: Conclusion
Based on the information gathered, the primary pollutants involved in the synthesis of photochemical smog are:
- Unsaturated hydrocarbons (e.g., ethene, benzene)
- Nitrogen dioxide (NO2)

### Final Answer
The primary pollutants used in the synthesis of photochemical smog are:
1. Unsaturated hydrocarbons
2. Nitrogen dioxide (NO2)