Major air pollutant is

Options

A. `CO_(2)`
B. `N_(2)`
C. `SO_(2)`
D. `CO`

Answer

### Step-by-Step Solution:

1. **Understanding Air Pollutants**: Air pollutants are substances in the air that can cause harm to humans and the environment. They can be gases, particulates, or biological molecules.

2. **Identifying Common Air Pollutants**: Common air pollutants include carbon dioxide (CO2), nitrogen oxides (NOx), sulfur dioxide (SO2), and carbon monoxide (CO). Each of these has different sources and effects on health and the environment.

3. **Evaluating Carbon Dioxide (CO2)**: While CO2 is a significant greenhouse gas contributing to global warming, it is not considered a major air pollutant in the context of immediate health effects. It is essential for photosynthesis but can become harmful in excess due to its role in climate change.

4. **Evaluating Nitrogen Oxides (NOx)**: Nitrogen oxides are harmful gases that can cause respiratory diseases and contribute to the formation of smog and acid rain. They are indeed serious pollutants but are not classified as the major air pollutant.

5. **Evaluating Sulfur Dioxide (SO2)**: Sulfur dioxide is known for causing acid rain and respiratory problems. It poses a significant environmental threat and can damage historical monuments, such as the Taj Mahal. However, it is not the most critical air pollutant.

6. **Identifying Carbon Monoxide (CO)**: Carbon monoxide is a colorless, odorless gas produced by incomplete combustion of fossil fuels. It is highly soluble in blood and binds with hemoglobin, preventing oxygen transport in the body, which can lead to carbon monoxide poisoning. This makes it particularly dangerous and a major air pollutant.

7. **Conclusion**: After evaluating the options, the major air pollutant is identified as carbon monoxide (CO).

### Final Answer:
The major air pollutant is **Carbon Monoxide (CO)**.

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