Suppose A is right, the champion is A or B, and B is wrong, then the champion must be C, then this assumption is wrong. Suppose B is right, the champion is definitely not C, C is wrong, D, E, F E and F can all be champions, so it is wrong. Suppose C is right and D is wrong, then the champion is not one of D, E, F E, F, the champion is A, B, C, A is wrong, the champion is not A, B, so the champion is C.