Answer: Option (c) is the correct answer.
Explanation:
When there is flow of energy in the form of electromagnetic waves in the space or without any medium then this type of energy is known as radiation.
For example, radiations from the Sun when fall on a metal plate then it becomes hot after sometime. This shows that energy is transferred from Sun to the metal plate.
Thus, we can conclude that the transfer of energy through empty space is called radiation.
