Which term is not a standard method of heat transfer?

• A. Conduction
• B. Convection
• C. Retraction
• D. Radiation

Answer: (C)

Heat moves from hotter to cooler areas through three established methods: conduction, which transfers energy through direct contact and molecular interaction in solids, liquids, and gases; convection, which involves the bulk movement of a fluid that carries energy along with it; and radiation, which transfers energy via electromagnetic waves and can occur through empty space or transparent media. Retraction is not a mechanism for transferring thermal energy—it's not a way heat moves. In HVAC contexts you’ll see conduction through metal ducts, convection as air streams circulating heat, and radiation from heaters, but there’s no heat-transfer method called retraction.