Two Conducting Spheres Are Made of the Same Material and Have

Two conducting spheres are made of the same material and have radii r and 2r. The spheres are placed a distance d > 2r from each other and have initial charges of -2Q and -4Q respectively. The point on the line connecting the centers of the two spherical shells where the electric potential is zero is

A) closer to -2Q.
B) closer to -4Q.
C) mid-distance between -2Q and -4Q.
D) There is no point on the line connecting the centers of the two spherical shells where the electric potential is zero.
E) More information is needed to work out the answer.