At theheight where it starts, just before it's dropped, the ball has some potential energy. The higher that spot is, the more potential energy the ball has. After the drop, whenever the ball is lower than the height from which it was dropped, it has less potential energy, and the missing potential energy shows up as kinetic energy ... motion.
This is the whole idea of the roller coaster. A machine drags it up to the top of the first hill, giving it lots of potential energy. After that, as long as it doesn't try to rise higher than the first hill, it never runs out of energy, and keeps going.
A). and B). The ball keeps going forward until it rises again to the same height it was dropped from ... on the other side. Then it stops and falls back.
C). The ball can never rise higher than the height it was dropped from. If the hump in the middle is the same height as the drop-height, then the ball stops right there, and falls back.
D). Same as B). As long as the track inside the loop is never higher than the droop-height, the ball just keeps going forward.
E). Same idea. Here it looks like the drop-height is the same as the top of the loop. The ball can't rise higher than it was dropped from, so it gets as far as the top of the loop and stops there. From there, I think it drops straight down from the top of the loop, instead of following the curve.
