Answer: Option (d) is the correct answer.
Explanation:
Radiation is defined as an electromagnetic energy which travels in space in the form of waves or particles.
This means that heat energy will always travel from a warmer object to a colder object.
For example, radiations coming from the Sun are able to transfer heat energy to the substance on which they fall.
Thus, we can conclude that radiation is the method of heat transfer used by the Sun.