The correct answer is C
A) I am pretty sure, by definition, all capacitors already contain a dielectric medium
B) The electric field across a capacitor (when at least partially charged) is uniform.
C) C = q/V
V = W/q
C = q*q/W
W = Fd
C = q*q/Fd
D) Increasing distance would cause capacitance to decrease
E) Current does not flow between the positively and negatively charged plates