Concept:Heat transfer through a vacuum occurs only by radiation, because radiation does not require a material medium.
Explanation:Conduction transfers heat through particle vibrations and collisions inside a solid or fluid, so it cannot occur in a vacuum.
Convection transfers heat by the bulk movement of heated particles in a fluid, so it also requires a fluid medium.
Radiation transfers heat as electromagnetic waves, such as infrared rays.
Electromagnetic waves can travel through empty space without needing air or any substance.
A vacuum is an empty space with no air or material particles to support conduction or convection.
Thus, heat can travel through a vacuum only by radiation.
Answer:C. Radiation only