A Parallel Plate Capacitor with Plates of Area a and Plate

A parallel plate capacitor with plates of area A and plate separation d is charged so that the potential difference between its plates is V. If the capacitor is then isolated and its plate separation is decreased to d/2, what happens to its capacitance?

A) The capacitance is twice its original value.
B) The capacitance is four times its original value.
C) The capacitance is eight times its original value.
D) The capacitance is one half of its original value.
E) The capacitance is unchanged.