Six people A. B, C, D, E, F participated in a final. Before the match, the three guessed: A: The champion is either A or B. B: The champion is C or D. C: D, E, F will never Probably the champion. After the game, it was found that only one of the three of them was correct, so who is the champion? ['A is the champion.', 'B is the champion.', 'C is the champion.', 'D is the champion.']