The atmosphere of the earth is heated by radiations which are mainly

Options

A. radiated by the sun
B. re-radiated by land
C. re-radiated by water
D. re-radiated by land and water

Explanation

To solve the question regarding how the atmosphere of the Earth is heated by radiations, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Radiation from the Sun**:
- The Sun emits energy in the form of radiation, which includes visible light, ultraviolet light, and infrared radiation. This energy travels through space and reaches the Earth.

2. **Absorption by Land and Water**:
- Once this solar radiation reaches the Earth's surface, it is absorbed by various components of the Earth, primarily land and water. This absorption causes the temperature of the land and water to increase.

3. **Re-radiation of Heat**:
- After the land and water absorb the solar energy, they do not retain all of it. Instead, they re-radiate some of this heat back into the atmosphere. This process of re-radiation is crucial for warming the air above the surface.

4. **Heating of the Atmosphere**:
- The heat that is re-radiated by the land and water warms the atmosphere. This is why the atmosphere is primarily heated by the energy that is re-radiated from the Earth's surface rather than directly from the Sun.

5. **Conclusion**:
- Therefore, the correct answer to the question is that the atmosphere of the Earth is heated by radiations which are mainly re-radiated by land and water.

### Final Answer:
The atmosphere of the Earth is heated by radiations which are mainly **re-radiated by land and water** (Option D).

---