Four charges of 1 mC, 2 mC, 3 mC, and – 6mC are placed one at each corner of the square of side 1m. The square lies in the x-y plane with its centre at the origin.

The electric potential is zero at the origin.

The electric potential is zero everywhere along the z-axis for any orientation of the square in the x-y plane.

The electric potential is not zero along the z-axis except at the origin

The electric potential is zero everywhere along the x-axis only of the sides of the square are parallel to x and y axis.