GKFix MCQ Question

What is the total potential at D before bringing the fourth charge, given charges at A(+q), B(-q), C(+q)?

• A. \frac{q}{4\pi\epsilon_0 d} \left(2 + \frac{1}{\sqrt{2}}\right)
• B. \frac{q}{4\pi\epsilon_0 d} \left(1 - \frac{1}{\sqrt{2}}\right)
• C. \frac{q}{4\pi\epsilon_0 d} \left(2 - \frac{1}{\sqrt{2}}\right)
• D. \frac{q}{4\pi\epsilon_0 d\sqrt{2}}