Answer: The correct answer is fluids.
Explanation:
There are 3 modes of heat transfer that happens:
1. Conduction: In this type of heat transfer, heat is transferred when there is direct contact between the two object.
2. Convection: In this type of heat transfer, heat is transferred when there is a movement of fluid (liquid or gas).
3. Radiation: In this type of heat transfer, heat is transferred when there is direct transfer of energy through space.
Hence, convection is only restricted to fluids which are liquids and gases.
