Answer: Varying amounts of the Moon's lit surface being visible from Earth.
Explanation:
Phases of the moon can be defined as the different shapes of the moon visible from the Earth. This happens because sun lits up the face of moon and due to different position of moon in the orbit around earth, varying portion of the lit surface of the moon is visible from Earth. Refer to the diagram below:
The roller coaster is stationary so the kinetic energy would be zero, but it is at the top of ramp so the potential energy would be high as its gravitational so it would have to be A