If the Distance Between Two Isolated Parallel Plates That Are

If the distance between two isolated parallel plates that are oppositely charged is doubled, the electric field between the plates is essentially unchanged. However, the:

A) charge on each plate will double.
B) force on a charged particle halfway between the plates will get twice as small.
C) potential difference between the plates will double.
D) force on a charged particle halfway between the plates will get four times as small.