Answer:
potential lines that are perpendicular to the electric field, they must be parallel to the plates
Step-by-step explanation:
A and C) for this drawing, as the electric field lines go from the positive plate to the negative plate and are horizontal to the potential lines that are perpendicular to the field, they must be parallel to the plates, see attached part a
B) in this case the ground has an energy of zero and the lines are parallel to the ground, see attached part b