There is a place where there are only gentlemen and villains. The gentleman only tells the truth and the villain only tells lies, but there is no difference in appearance. Ask A: "There must be a gentleman among you two?" A said, "No. ". Please judge who they are? ? ['A is a gentleman, B is a villain.', 'A and B are gentlemen.', 'A and B are villains.', 'A is a villain, B is a gentleman.']