The layer that the heated material moves would be C. Mantle.
What is the Earth's mantle ?
The mantle is a layer of hot, molten rock that lies beneath the Earth's crust. The heated material in the mantle is constantly moving and circulating, which creates convection currents. These convection currents push against the tectonic plates, causing them to move.
The inner core is a solid, metal sphere that lies at the center of the Earth. The outer core is a liquid metal layer that surrounds the inner core. The crust is the outermost layer of the Earth and is made up of solid rock.