Which of the following is true for a system consisting of a mass oscillating on the end of an ideal spring?

a. the kinetic and potential energies are equal at all times.
b. the kinetic and potential energies are both constant.
c. the maximum potential energy is achieved when the mass passes through its equilibrium position.
d. the maximum kinetic energy and maximum potential energy are equal, but occur at different times.
e. the maximum kinetic energy occurs at maximum displacement of the mass from its equilibrium position.