Work Step by Step
The potential near the positive charge is positive and vice-versa. Thus, a point in region B will have 0 potential. When we move far away, it will act as a single point charge of $-3uC$ , giving negative potential. Thus, a point in region A will have 0 potential too. The electric field can be 0 only in region A, and this won't occur at the same point where potential is 0.