Answer:
The correct answer is D, V =0
Step-by-step explanation:
The electrical potential due to a point charge is given by
V = k ∑

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