In an isolated parallel plate capacitor of capacitance C the four surfaces have charges `Q_(1), Q_(2), Q_(3)` and `Q_(4)` as shown in the figure. The potential difference between the plates is :
A. `(Q_(1)+Q_(2))/(C)`
B. `|(Q_(2))/(C)|`
C. `|(Q_(3))/(C)|`
D. `(1)/(C) [(Q_(1)+Q_(2))-(Q_(3)-Q_(4))]`