The four couples A. B, C and D participated in a ballroom dance. In the beginning, the four gentlemen's partners had their wives. Later, they exchanged their partners three times: ① Mr. B and Mr. C exchanged their dance partners; ② Mr. A Exchange dancing partners with Mr. C; ③ Mrs. B and Mrs. Ding exchange partners. Q After three exchanges of dance partners, which of the following dance pairs is correct? ['Mr. A and Mrs. Ding.', 'Mr. C and Mrs. B.', 'Mr. C and Mrs. Ding.', 'Mr. Ding and Mrs. A.']