Which method of heat transfer requires a medium and involves actual physical movement of particles?

Heat transfer methods differ fundamentally in whether they require a medium and whether particles physically move. Option A (Conduction) is incorrect — conduction requires a medium but the particles do NOT physically move from their positions. Option B (Radiation) is incorrect — radiation does NOT require a medium and involves no movement of particles. Radiation travels as electromagnetic waves through vacuum. Option C (Convection) is CORRECT — convection requires a medium AND involves the actual physical movement of heated particles from one place to another. When a liquid or gas is heated, the heated portion becomes less dense, rises, the cooler denser portion sinks, and a convection current is established. The particles themselves physically move, carrying thermal energy with them. Option D (All three methods) is incorrect — only convection satisfies both conditions (needs medium AND particles move). Conduction needs medium but no particle movement. Radiation needs no medium and no particle movement.