The most effective greenhouse gas is

Options

A. CFC
B. `CO_(2)`
C. Methane
D. `O_(2)`

Answer

**Step-by-Step Solution:**

1. **Understanding Greenhouse Gases**: Begin by defining what greenhouse gases are. Greenhouse gases are gases that trap heat in the Earth's atmosphere, contributing to the greenhouse effect, which warms the planet.

2. **Temperature Without Greenhouse Gases**: Recognize the significance of greenhouse gases by noting that without them, the Earth's average temperature would be approximately -18 degrees Celsius.

3. **Temperature With Greenhouse Gases**: Acknowledge that the presence of greenhouse gases raises the average temperature to about +15 degrees Celsius, demonstrating their critical role in maintaining a habitable climate.

4. **Examples of Greenhouse Gases**: Identify common greenhouse gases. Examples include:
- Carbon Dioxide (CO2)
- Methane (CH4)
- Chlorofluorocarbons (CFCs)
- Water Vapor (H2O)

5. **Determining the Most Effective Greenhouse Gas**: Discuss which greenhouse gas is the most effective. Water vapor (H2O) is identified as the most effective greenhouse gas due to its ability to trap heat efficiently.

6. **Identifying the Second Most Effective Greenhouse Gas**: Since water vapor is not always present in significant amounts, methane (CH4) is recognized as the second most effective greenhouse gas.

7. **Conclusion**: Conclude that the most effective greenhouse gas is water vapor, while methane is the second most effective.

**Final Answer**: The most effective greenhouse gas is water vapor (H2O), with methane (CH4) being the second most effective.

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