Radiation is defined as the transfer of heat energy through electromagnetic waves, which can occur in a vacuum.

• A. The transfer of heat through direct contact.
• B. The transfer of heat through the movement of fluids.
• C. The transfer of heat energy through electromagnetic waves, which can occur in a vacuum.
• D. The transfer of heat by conduction through solids.

Answer: (C)

Heat can move in three ways: conduction, convection, and radiation. Radiation is the transfer of heat energy by electromagnetic waves and does not require matter to carry it, so it can happen through empty space. This is why sunlight can warm Earth even though space is a vacuum. In contrast, conduction needs direct contact between particles in a solid, and convection depends on the movement of fluids; both require a medium. So the statement correctly identifies radiation as heat transfer through electromagnetic waves that can occur in a vacuum.