Answer
The correct answer is:
(b) B and C
Work Step by Step
Lines of equal potential cross electric field lines at $90^{\circ}$ angles. If we connect point B and point C with a straight line, the line will cross the electric field lines at approximately $90^{\circ}$ angles. This is not true if we connect any other pair of points labeled in the diagram.
The correct answer is:
(b) B and C