Major cause of air pollution in big cities is

Options

A. domestic exhaust
B. automobile exhaust
C. burning of cooking gas
D. thermal power plant

Answer

**Step-by-Step Solution:**

1. **Understanding Air Pollution**: Air pollution is defined as the presence of harmful substances in the atmosphere that can adversely affect health, climate, and the environment. Common air pollutants include ammonia, carbon dioxide, carbon monoxide, various nitrogen oxides, particulate matter, and hydrocarbons.

2. **Identifying Sources of Air Pollution**: In big cities, there are multiple sources of air pollution. The question provides several options: domestic exhaust, automobile exhaust, burning of cooking oil, and thermal power plants.

3. **Evaluating Each Option**:
- **Domestic Exhaust**: This refers to emissions from household activities. While it contributes to air pollution, it is not a major source in large urban areas.
- **Automobile Exhaust**: This is the exhaust emitted from vehicles. Given the high population density and the number of vehicles in big cities, this is a significant contributor to air pollution.
- **Burning of Cooking Oil**: This is generally a minor source of air pollution, especially in urban settings where modern cooking methods are prevalent.
- **Thermal Power Plants**: While they do contribute to air pollution, they are often located on the outskirts of cities and do not have as significant an impact on urban air quality compared to automobile emissions.

4. **Conclusion**: After evaluating all the options, it is clear that the major cause of air pollution in big cities is **automobile exhaust**.

5. **Final Answer**: The correct answer is **automobile exhaust**.

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