Which Statements Must Be True About the Surface of a Charged

Which statements must be true about the surface of a charged conductor in which no charge is moving? (There could be more than one correct choice. )

A) The electric field is zero at the surface.
B) The electric potential of the surface is zero.
C) The electric field is constant at the surface.
D) The electric potential is constant over the surface.
E) The electric field is perpendicular to the surface.