Two lab carts are on a frictionless track, attached by a spring. The carts are pushed together by a student in a Physics lab, compressing the spring fully. The student lets go of the carts and they move in opposite directions as the spring extends. Which of the following statements describes what happens to the car/spring system after the cars are released?
A. The kinetic energy remains constant.
B. The kinetic energy increases.
C. The momentum remains constant.
D. The momentum increases.