Which of the following is not a greenhouse gas?

Options

A. `CO_(2)`
B. `CH_(4)`
C. `CCl_(2)F_(2)`
D. `O_(2)`

Answer

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

### Step-by-Step Solution:

1. **Define Greenhouse Gases**: Greenhouse gases are substances that can absorb and emit infrared radiation, contributing to the greenhouse effect. This effect leads to an increase in the Earth's temperature.

2. **List Common Greenhouse Gases**: Some common greenhouse gases include:
- Water vapor (H2O)
- Carbon dioxide (CO2)
- Methane (CH4)
- Nitrous oxide (N2O)
- Ozone (O3)
- Chlorofluorocarbons (CFCs)

3. **Analyze the Options**: The question provides several options to choose from. We need to identify which one is not a greenhouse gas:
- Option A: CO2 (Carbon Dioxide) - This is a greenhouse gas.
- Option B: Methane (CH4) - This is a greenhouse gas.
- Option C: Chlorofluorocarbons (CFCs) - This is a greenhouse gas.
- Option D: CCl2F2 (Dichlorodifluoromethane) - This is a type of CFC and is also a greenhouse gas.
- Option E: Oxygen (O2) - This is not a greenhouse gas.

4. **Conclusion**: Based on the analysis, the option that is not a greenhouse gas is **Oxygen (O2)**.

### Final Answer:
**Oxygen (O2) is not a greenhouse gas.**

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