Answer: An equipotential surface must be perpendicular to the electric field at every point. The correct option is B.
Explanation: Equipotential surface is any surface over which the potential difference is constant. Examples include:
-The surface of a conductor in electrostatic field.
- surface of a liquid in equilibrium.
Equipotential surface are perpendicular to the electric field at every point because components of electric field intensity along the surface is zero ( this is because no work is done while moving a charge from one point to another on an equipotential surface).