6 people A. B, C, D, E, F participated in a final game. Before the match, there were 3 guesses. First, the champion is either A or B. Second, the champion is C or D. Third, D, E, F never probably be the champion. Only one of the three was correct after the match. So who is the champion? ['A is the champion.', 'B is the champion.', 'C is the champion.', 'D is the champion.']