The correct answer is convection
In liquids and gases, convection is the most prominent method for the transfer of energy or heat. Convection is caused by the movement of the hotter particles to a region of colder particles takes place. This results in making the whole liquid or gas hot or warm.
Example: The water bubbles in boiling water moves from bottom to the top of the pan to cover the colder water present at the top.
This is because of convection.