At any point on the right bisector of the line joining two equal and opposite charges: 1)the electric field is zero2) the electric potential is zero3) the electric potential decrease with increasing distance from the center4) the electric field is perpendicular to the line joining the charges b

Dear student,

The distance of any point on the perpendicular bisector of line joining the two charges to the two charges is equal.
Since electric potential is a scalar quantity and hence adds scalarly, the sum of electric potentials due to both the charges along the perpendicular bisector is zero.