simple harmonic motion equations

Question

It is possible to tell theoretically if a mechanical motion will be SHM through a careful analysis of the forces in the system. An object will execute SHM with displacement coordinate x.

A: all the forces involving x are conservative.

B: the total force can be equated with -kx.

C: all the forces involving x have equal and opposite reactions.

D: the sum of all the forces involving x is zero

E: the total force on the object is always zero.