The answer is B. It is B because in if convection currents cooled down then the earth would die.
Answer: Molten materials
The convection can be defined as the heat transfer in liquid. The liquid inside the earth moves in a circular motion and in this way heat transfer takes place.
The hotter liquid moves up and the cold liquid takes place of the hotter particles and it looks exactly like a circular movement of liquids.
The movement of molten material is driven by the heat inside the earth.
