47. Two charges, -2 Q and +Q , are located on the x -axis, as shown above. Point P , at a distance of 3 D from the origin O , is one of two points on the positive x -axis at which the electric potential is zero. How far from the origin O is the other point?
(A) 2/3D
(B) 3/2D
(C) 5/3D
(D) 2 D