50 POINTS! please help asap!

Two point charges, each of magnitude +a, are separated by a distance d. Refer to the diagram for a model of the point charges.

The point charges are allowed to move in the electric field that they generate. Which describes their movement and change in electric potential energy?
A: They move toward each other, and their electric potential energy increases.
B: They move away from each other, and their electric potential energy decreases.
C: They move toward each other, and their electric potential energy decreases.
D: They move away from each other, and their electric potential energy increases.