Three Infinite Planes of Charge, A, B and C, Are

Multiple Choice

Three infinite planes of charge, A, B and C, are vertical and parallel to one another. There is a uniform electric field to the left of plane A and a uniform electric field to the right of plane C. The field points to the left and the field points to the right. The signs of the charges on plates A, B and C may be

A) −, −, −.
B) +, −, −.
C) +, −, +.
D) +, +, +.
E) any one of the above.