When mantle rocks near the radioactive core are heated, they become less dense than the cooler, upper mantle rocks. These warmer rocks rise, while the cooler rocks sink. This movement of warmer and cooler mantle rocks creates pockets of circulation within the mantle called _________, which are thought to be the force behind the movement of tectonic plates over the asthenosphere.
A) magma flows
B) density cells
C) convection cells (currents)
D) conduction points