Final answer:
The rate of heat transfer by radiation does not require a medium to propagate.
Step-by-step explanation:
The rate of heat transfer by radiation is best described by the statement that it does not require a medium to propagate. Radiation is the only method of heat transfer where no medium is required, meaning that the heat doesn't need to come into direct contact with or be transported by any matter. It can transfer heat through empty space, such as the electromagnetic radiation emitted by the sun warming the Earth.