Charge Concentration on Capacitors

The other day I was filling out an online quiz our professor assigned for our physics class. The question below was on the quiz. I don't need help answering it, but was wondering if anyone could help explain to me what this question is saying. Talking to my professor proved to have only confused me more. While he managed to give me a brief explanantion as to why the answer was E, I still didn't quite fully understand why. According to my understanding, equipotential lines are just graphical representations of pathways of equal Voltage. Having a higher "density" of equipotential lines therefore, didn't make sense. After all, aren't there technically infinite amounts of equipotential lines? I had the same reasoning for field lines.

My original answer was A, but having had two tries to answer (and A being wrong) I put none of the above.

The charge concentration on the edges of a capacitive plate are

A) higher because tangential forces on the charges force more charges to group together
B) lower because the field lines are not straight.
C) higher as evidenced by a higher density of equipotential lines.
D) higher as evidenced by a higher density of field lines.
E) answers a), c) and d)
F) answers a) and c)
G) none of the above.

ANSWER: E

We did a lab on field lines and equipotential lines, where we mapped the voltage at certain points and then created a plot (see attached.)