Answer: Convection
Step-by-step explanation: The heat transfer takes place by three modes:
1. Conduction: This type of heat transfer happens when there is direct contact between two objects.
2. Convection: This type of heat transfer happens when there is a movement of fluid (liquid or gas) in which convection currents are produced due to the movement of hot fluid upwards and cold fluid downwards. This happens as the density of hot fluid decreases and thus it moves upwards.
3. Radiation: This type of heat transfer happens when there is direct transfer of energy through space.