Surface of earth is kept warm by
(a) Solar radiations
(b) Geothermal energy
(c) Green houses flux
(d) Absorption of infrared radiations by green house gases

Options

A. Solar radiations
B. Geothermal energy
C. Green houses flux
D. Absorption of infra red radiations by green house gases

Answer

To solve the question "Surface of earth is kept warm by," we need to analyze each of the given options and determine which one is the most accurate.

### Step-by-Step Solution:

1. **Understanding Solar Radiation (Option A)**:
- Solar radiation refers to the energy emitted by the sun. It reaches the Earth and is absorbed by the surface, which helps in warming it.
- However, while solar radiation is essential for warming the Earth, it is not the only factor that keeps the surface warm.

**Hint**: Consider the role of solar radiation in warming the Earth but look for additional mechanisms that maintain this warmth.

2. **Evaluating Geothermal Energy (Option B)**:
- Geothermal energy is the heat that comes from the Earth’s interior. It contributes to the temperature of the Earth's surface but is not the primary source of warmth.
- It is localized and not a significant factor in the overall warming of the Earth's surface compared to solar energy.

**Hint**: Think about the sources of heat that are more widespread and influential in warming the Earth's surface.

3. **Analyzing Greenhouse Flux (Option C)**:
- Greenhouse flux refers to the process by which greenhouse gases trap heat in the Earth's atmosphere. This is a crucial mechanism for maintaining the Earth's temperature.
- Greenhouse gases absorb and re-radiate infrared radiation, preventing heat from escaping back into space, thus keeping the surface warm.

**Hint**: Focus on how greenhouse gases interact with solar radiation and their role in maintaining the Earth's temperature.

4. **Considering Absorption of Infrared Radiation by Greenhouse Gases (Option D)**:
- This option is closely related to the greenhouse effect. Greenhouse gases absorb infrared radiation emitted from the Earth's surface and trap heat.
- While this process is important for keeping the Earth warm, it is part of the broader greenhouse effect, which is described in Option C.

**Hint**: Reflect on whether this option is a specific aspect of a more general process described in another option.

### Conclusion:
After analyzing all the options, the correct answer is **(c) Greenhouse flux**. This option encompasses the overall process of how greenhouse gases trap heat and maintain the Earth's temperature.