What force causes warm molten rock to move upward in the mantle?

a. Convection

c. Refraction

b. Radiation

d. Conduction

The answer is A. Convection.

Warm air is less dense than cold air. In something like a room heated by a fireplace, the warm air is pushed up by colder air. It's then cooled and comes back down. The same principle applies to molten rock in the mantle. Slightly cooler pockets push up the warmer ones.

It is called convectiojn zones