Smog the occurs mainly by automobile exhausts at high temperature over congested metropolitan cities due to still air is called

Options

A. London smog
B. Classical smog
C. Both (1) and (2)
D. Photochemical smog

Answer

To solve the question regarding the type of smog that occurs mainly due to automobile exhausts at high temperatures over congested metropolitan cities, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the term "smog":**
- Smog is a combination of smoke and fog. It typically occurs in urban areas where there is a high concentration of pollutants.

2. **Identify the sources of smog:**
- The question specifies that the smog is caused mainly by automobile exhausts. This indicates that the pollutants are primarily from vehicles.

3. **Differentiate between types of smog:**
- There are different types of smog, primarily:
- **London smog:** This type is associated with industrial emissions and is rich in sulfur compounds.
- **Photochemical smog:** This type is formed when sunlight reacts with pollutants such as nitrogen oxides and volatile organic compounds, primarily from automobile emissions.

4. **Consider the conditions mentioned in the question:**
- The question states that this smog occurs at high temperatures over congested metropolitan cities. Photochemical smog typically forms under these conditions, especially in the presence of sunlight.

5. **Conclude with the correct answer:**
- Given that the smog in question is primarily caused by automobile exhausts and occurs in urban areas with high temperatures, the correct answer is **photochemical smog**.

### Final Answer:
The type of smog that occurs mainly by automobile exhausts at high temperatures over congested metropolitan cities is called **photochemical smog**.

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