An example of the transmission of heat by conduction is

• A. Diathermy
• B. Hot water bottle
• C. Ultrasound
• D. Microthermy

Answer: (B)

Conduction is heat transfer through direct contact from a hotter object to a cooler one. A hot water bottle sits in contact with the skin and is warmer than the skin, so heat flows from the bottle into the body across that contact surface. This direct transfer of heat by touch is the essence of conduction in a therapeutic context. The other options involve different energy delivery methods: diathermy heats tissue with electromagnetic energy rather than through surface contact, ultrasound uses high-frequency sound waves to generate heat inside tissues, and microthermy relies on another energy delivery mechanism rather than simple surface conduction.