Final answer:
At the peak of a roller coaster, the train has maximum potential energy and minimal kinetic energy, so the correct answer is 0% kinetic and 100% potential energy.
Step-by-step explanation:
When a roller coaster train is at the top of the highest peak, it has primarily stored potential energy (PE) due to its elevated position. As the roller coaster is about to descend, its speed is minimal, so the kinetic energy (KE) is relatively low. According to the law of conservation of energy, in the absence of external forces like friction and air resistance, all the potential energy will convert into kinetic energy as the coaster descends. However, at the very top, before descent, potential energy is at its maximum while kinetic energy is at or close to its minimum. Therefore, the correct answer is E.0% kinetic, 100% potential energy since the coaster is momentarily at rest before the drop.