Concept:Solar energy is a form of heat transfer that reaches the Earth across empty space purely through radiation.
Explanation:The Sun continuously emits energy in the form of electromagnetic waves, which carry solar radiation.
These waves travel through the near-vacuum of space, covering about 150 million kilometres, before reaching the Earth.
Unlike conduction and convection, radiation does not require any material medium, so the emptiness of space does not stop it.
Conduction needs direct contact between substances, and convection depends on the movement of fluids such as air or water.
Because neither conduction nor convection can operate across empty space, they cannot carry the Sun's energy to the Earth.
When the solar radiation strikes the Earth's surface, it is absorbed and changed into heat, warming the surface.
Hence, the warming of the Earth's surface by the Sun happens through radiation.
Answer:D. Radiation