What method of energy transfer is represented by radiation?

Radiation is best understood as the transfer of energy through electromagnetic waves, which can occur without the need for a medium. This means that radiation can happen even through a vacuum, like the way sunlight reaches the Earth. In this context, it involves energy moving in the form of rays or waves, such as infrared radiation, which is commonly associated with heat transfer.

On the other hand, circulation of fluids pertains to convection, which involves the movement of liquid or gas, transferring heat as they move. Transfer through physical contact relates to conduction, where heat is directly passed between materials that are touching. Movement of solids in combustion describes a physical process that relates to the chemical reaction of materials burning, which does not fit the definition of radiation. Thus, the correct answer clearly highlights the unique nature of energy transfer represented by radiation.