A. If a miracle happened, we couldn't have sufficient evidence to prove that it had | B. The notion of a miracle is incoherent | ||
C. Miracles can't happen | D. Not even God can break the necessary connexions in nature | ||
D is definitely out, because Hume thinks there aren't any necessary connexions in nature.
C is out because 'can't' expresses an alleged impossibility, and for Hume anything can happen. (To say some things are possible and some things aren't is to commit yourself to the mistaken view (according to Hume) that there are necessary connexions in nature.)
B seems the best answer. It argues that the idea of a miracle involves holding two propositions together:
(a) there is a universal law of nature; and
(b) x, which would, if it had happened, be inconsistent with that universal law, has in fact happened.
A is not Hume's point because it would commit him to accepting that the notion of a miracle is coherent.