The transfer of heat from a higher temperature to a lower temperature occurs due to the actual mass movement of the molecules:

The correct answer is Convection.

Key Points

Convection

• It is heat transfer by the movement of its molecules.
• It occurs only in fluids (liquid and gas) not in solids because solid particles can not move from one place to another.
• For example, in a pot boiling water on the stove, or in thunderstorms, where hot air rises to the base of the clouds.

Additional Information

Conduction: 

• The heat transfer through direct physical contact is known as conduction.
• Heat transferred from one end to the other end is called conduction. 
• Heat transfer through conduction can only happen in conductors of heat like iron, copper etc. 
• Heat transfer does not take place across insulators like wood, plastic etc. 

Radiation: 

• When electromagnetic radiation is emitted or absorbed to transfer the heat or When heat is transferred in the form of electromagnetic waves is known as radiation.
• Electromagnetic radiation includes microwaves, radio waves, infrared radiation, visible light, ultraviolet radiation, gamma rays, and X-rays.
• The method does not require any medium so heat from the sun reaches us by this method.

Confusion Points

• The process by which heat is transferred from the hotter end to the colder end of an object is known as conduction. 
• In convection, heat transfer takes place through the transfer of molecules while radiation takes place through electromagnetic waves.