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.

The statement which indicates that the clump of waxy fluid at the center of the lamp is moving downward rather than upward is the statement stated in option D. The correct option is D. The lamp has a heat source at the base, which increases the temperature of the waxy fluid making it to melt and move downward.

You need to be more specific.  i really don't know what a "motion map" is.you can draw a graph of an object's position, distance, displacement, speed,velocity, or acceleration versus time, or you can draw a graph of the object's x-position versus its y-position and not give any information about time at all.if the graph presents position or displacement against time,  then constant velocity is a straight line . . i.e. a line that has  constant slope.if the graph shows speed against time, then constant velocityis a horizontal piece of line.if the graph shows acceleration against time, then constant  velocity is a piece of line that lies on the x-axis . . it's value is zero.