The reason for green-house effect is

Options

A. Higher `CO_(2)` concentration causing global warming
B. Absorption of infra-red rays by gases and dust particles
C. Both A and B
D. Rarefaction of `CO_(2)`

Answer

### Step-by-Step Solution:

1. **Understanding the Greenhouse Effect**:
- The greenhouse effect is a natural process that warms the Earth's surface. It occurs when the Sun's energy reaches the Earth and is partially reflected back to space, while the rest is absorbed and re-radiated by greenhouse gases.

2. **Identifying Greenhouse Gases**:
- Important greenhouse gases include water vapor (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ozone (O3). These gases play a crucial role in maintaining the Earth's temperature.

3. **Analyzing the Options**:
- **Option 1**: Higher CO2 concentration causing global warming - This is related to the enhanced greenhouse effect but does not directly explain the greenhouse effect itself.
- **Option 2**: Absorption of infrared rays by gases and dust particles - This accurately describes the mechanism of the greenhouse effect.
- **Option 3**: Both A and B - Since option A is not correct in the context of the greenhouse effect, this option is also not valid.
- **Option 4**: Rare fraction of CO2 - This does not explain the greenhouse effect.

4. **Conclusion**:
- The most accurate reason for the greenhouse effect is **Option 2: Absorption of infrared rays by gases and dust particles**. This describes the fundamental process that leads to the warming of the Earth.

### Final Answer:
The reason for the greenhouse effect is the absorption of infrared rays by gases and dust particles.

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