Questions 37-38 refer to five different charge configurations on the xy-plane using two or four point charges of equal magnitude having signs as indicated below. All charges are the same distance from the origin. The electric potential infinitely far from the origin is defined to be zero.
38. In which configuration is the value of the electric field at tile origin equal to zero, but the electric potential at the origin not equal to zero?
(A) A
(B) B
(C) C
(D) D
(E) E