The lava lamp has a light bulb as a heat source at its base. the lamp contains a colored, waxy fluid that can be observed moving in clumps through a clear liquid.

which indicates that the clump of waxy fluid at the center of the lamp is moving downward rather than upward?

it is less dense than the surrounding liquid.
its molecules are losing kinetic energy.
its molecules begin to slow down before they become faster.
its temperature increases before it decreases again.