Which of the following is not a greenhouse gas

Options

A. `CO_2`
B. `O_2`
C. `CH_4`
D. Water vapour

Answer

To determine which of the following is not a greenhouse gas, we need to first identify the common greenhouse gases and then compare them with the options provided.

### Step-by-Step Solution:

1. **Understanding Greenhouse Gases**:
Greenhouse gases are substances that can absorb and emit infrared radiation. This process contributes to the greenhouse effect, which warms the Earth's surface. Common greenhouse gases include:
- Water vapor (H2O)
- Carbon dioxide (CO2)
- Methane (CH4)
- Nitrous oxide (N2O)
- Ozone (O3)

2. **Analyzing the Options**:
We need to analyze the options given in the question to identify which one is not a greenhouse gas. Let's consider the common gases:
- **CO2 (Carbon Dioxide)**: This is a well-known greenhouse gas.
- **O3 (Ozone)**: This is also a greenhouse gas, particularly in the upper atmosphere.
- **CH4 (Methane)**: This is another significant greenhouse gas.
- **O2 (Oxygen)**: This is not a greenhouse gas as it does not absorb infrared radiation.

3. **Identifying the Correct Answer**:
From the analysis, we can conclude that among the gases listed, **O2 (Oxygen)** is not a greenhouse gas. Therefore, the answer to the question "Which of the following is not a greenhouse gas?" is **O2**.

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

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