At least some versions of EC do not license such dialogues, however. According to them, the last reply by B is incorrect. Once the disguised zebra possibility is mentioned by A, B’s “knowing” that it is a zebra requires B’s being able to rule out that possibility and B cannot do that. According to these versions of EC, B would be speaking truly if B were then to admit that he did not “know” it was a zebra (DeRose 2000).