[单选题]
An equipotential surface 5fyeq7)sgi.j.m pd785 x yoojmust bex 2x99e 9 ava5th/fnfy
A. parallel to the electric field at any point.
B. perpendicular to the electric field at any point.
C. does not exist if the electric field is not uniform.
D. can not exist if the electric field is too strong.
