Among the following the one which is not a 'greenhouse gas' is

Options

A. `N_2O`
B. `CO_2`
C. `CH_4`
D. `O_2`

Answer

To determine which of the following options is not a greenhouse gas, we need to understand what greenhouse gases are and identify the options given.

### Step-by-Step Solution:

1. **Understanding Greenhouse Gases**: Greenhouse gases are substances that trap heat in the atmosphere. They contribute to the greenhouse effect, which warms the Earth.

2. **Common Greenhouse Gases**: Some common examples of greenhouse gases include:
- Carbon Dioxide (CO2)
- Methane (CH4)
- Nitrous Oxide (N2O)
- Chlorofluorocarbons (CFCs)

3. **Identifying the Options**: The question likely provides a list of gases. We need to analyze each option to see if it fits the definition of a greenhouse gas.

4. **Evaluating Each Gas**:
- **Carbon Dioxide (CO2)**: This is a well-known greenhouse gas.
- **Methane (CH4)**: This is also a significant greenhouse gas.
- **Chlorofluorocarbons (CFCs)**: These are synthetic compounds that are potent greenhouse gases.
- **Sulfur Dioxide (SO2)**: This is not a greenhouse gas; it contributes to acid rain and has a cooling effect on the atmosphere.

5. **Conclusion**: Based on the evaluation, the gas that is not a greenhouse gas among the options is **Sulfur Dioxide (SO2)**.

### Final Answer:
The one which is not a greenhouse gas is **Sulfur Dioxide (SO2)**.

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