Answer: The correct answer is Option A.
Step-by-step explanation:
Heat transfer is defined as the process in which heat is transferred from high temperature to low temperature to maintain equilibrium.
There are 3 modes by which heat can be transferred, they are:
- Conduction: This mode of heat transfer occurs whenever a direct contact between two object happens.
- Convection: This mode of heat transfer occurs whenever a movement of fluid (liquid or gas) takes place.
- Radiation: This mode of heat transfer occurs whenever a direct transfer of energy through space happens.
Thus, all these three modes involve the heat flow from hot objects to cold objects.
Hence, the correct answer is Option A.