Answer:
The correct answer is D, Â Â V =0
Explanation:
The electrical potential due to a point charge is given by
    V = k ∑ [tex]q_{i} / r_{i}[/tex]
Let's apply this equation to our case
    V = k (Q / r - Q / r)
    V = 0
Since the two charges have the same magnitude and are of opposite signs and the distance from any corner to the center of the square from side to is
     r =  √2  a/2
Therefore all distances are equal
The correct answer is D