I am working off the second image you attached, specifically am looking at the roller coaster ride depicted there, having two hills (first higher) and one valley.
(a) The greatest potential energy (Ep) is on top of the first hill. The greatest kinetic energy (Ek) is found in the valley. I am assuming they are asking for the two extremes at separate spots.
(b) The smallest Ep of the cart is found when it is in the valley. The smallest Ek is found at the top of the first hill (right before it starts moving)
(c) If "falls" refers to the ride moving downhill, then the following changes occur: Ep is going down (decreasing), Ek is going up (increasing).
(d) the sum of Ek and Ep, aka total mechanical energy, remains constant.
