Greenhouse gases are

Options

A. Absorber of long-wave radiations from the earth
B. Transparent to both solar radiations and long-wave radiations from the earth
C. Absorber of solar radiations for warming the atmosphere
D. Transparent to emissions from the earth for passage into outer space

Answer

### Step-by-Step Solution:

1. **Understanding Greenhouse Gases**:
- Greenhouse gases are gases in the Earth's atmosphere that trap heat. They include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and water vapor (H2O).

2. **Function of Greenhouse Gases**:
- These gases primarily absorb long-wave (infrared) radiation emitted from the Earth's surface. This absorption prevents heat from escaping into space, thus warming the atmosphere.

3. **Transparency to Solar Radiation**:
- Greenhouse gases are generally transparent to incoming solar radiation (short-wave radiation) but absorb outgoing long-wave radiation. This characteristic allows sunlight to enter the atmosphere but traps heat.

4. **Impact on Earth's Temperature**:
- The increase in concentration of greenhouse gases enhances the greenhouse effect, leading to an increase in Earth's average temperature, a phenomenon known as global warming.

5. **Consequences of Global Warming**:
- The rise in temperature can lead to various environmental issues, including melting glaciers, rising sea levels, and changes in weather patterns.

6. **Conclusion**:
- Given the functions and characteristics of greenhouse gases, the correct answer to the question "Greenhouse gases are..." is that they are "absorbers of long-wave radiations from the earth."