Yes on both A and C. My explanation for A would be that work needs to be done to push a positive test charge from B to A against the force of the electric field. Your V=kq/r is obscure (unrelated to this question) because it is the absolute potential or work/charge for moving a charge from infinite distance into a position that is distance r away from charge q. It does tell you that the potential midway between the positive and negative plates is zero, though.
and the other answers are wrong, correct?
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