Answer
a. D, B, C, E, A
b. D, B, C, E, A
c. A, E, C, B, D
Work Step by Step
a and b. KE is $\frac{1}{2}mv^{2}$. The ball is moving fastest at point D where it has dropped the most, and has the most KE there.
It is moving slowest at point A and has the least KE there.
The speed of the roller coaster car at each point, ranked from greatest to least, is the same as the height at each point, ranked from lowest to highest: D, B, C, E, A.
c. PE + KE = constant.
PE is greatest where KE is least, and PE is the least where KE is the greatest.