The diagram shows a roller coaster track. Assume that the system is closed. At point D, the roller coaster car is upside down at the top of the vertical loop.

which statement best describes potential and kinetic energies of the roller coaster at point D?

A. Kinetic energy is at its maximum, and potential energy is about 50%.

B. both kinetic energy and potential energy are at their maximum‘s.

C. both kinetic energy and potential energy are at their minimum‘s.

D. both kinetic energy and potential energy are about 50%.