The correct answer is option 2: Insolation. Insolation refers to the solar radiation that reaches the Earth`s surface. It is a combination of the words "incoming" and "solar radiation." Insolation plays a crucial role in various natural processes such as photosynthesis, evaporation, and the Earth`s climate system. Option 1, Radiant energy, refers to the energy that is emitted or transmitted in the form of electromagnetic radiation. Option 3, Sunshine, is a commonly used term to describe the light and warmth that is felt from the Sun. Option 4, Terrestrial radiation, refers to the radiation emitted by the Earth`s surface as heat energy.