Heat reaches earth by which of the following process?

Radiation

The correct answer is option 3. Radiation.

Heat reaches the Earth primarily through the process of radiation.

While conduction and convection also play roles in heat transfer, radiation is the primary mechanism by which the Sun's energy reaches the Earth. The Sun emits electromagnetic radiation, including visible light, which travels through the vacuum of space and reaches the Earth. Once this radiation interacts with the Earth's atmosphere and surface, further processes like conduction and convection come into play to distribute and transfer heat within the Earth's systems.