GKFix MCQ Question

What is the potential at point C due to the charge at A, given the diagonal distance is d√2?

• A. \frac{-q}{4\pi\epsilon_0 d\sqrt{2}}
• B. \frac{+q}{4\pi\epsilon_0 d\sqrt{2}}
• C. \frac{+q}{4\pi\epsilon_0 d}
• D. Zero