As a chem major, I can say that it is absolutely without a doubt not B. I would imagine it is A, since this molecule will dissociate completely into ions. I don't think C dissociates appreciably, either.
Just wanted to add that it must be A because AgCl is pretty insoluble--don't confuse it with NaCl. All chlorides are 100% soluble except Ag, Hg and Pb.