[单选题]
Four point charges are placed as shown on thekagh2v n;e *;f corners of a(d7pe2zwui(z ja x- b;ny7p5e square. Charges of +2Q and −Q, ax2-7p5;eu wa7d zzy bj(ni (pend unknown charges A and B are located as shown on the diagram.
At the center of the square, the total potential is zero, but the resultant electric field is not zero.
Which of the following is a possible combination for the charges A and B?
A. A is +2Q ; B is -3Q
B. A is +2Q ; B is -Q
C. A is -Q ; B is +2Q
D. A is +2Q ; B is +Q
