21.Professor Li has      interest in history, especially in       history of Ming Dynasty.

A. an; x ¡¡¡¡¡¡  B. an; the ¡¡¡¡¡¡C. x; the ¡¡¡¡    ¡¡D. x; an

22. The accident happened on such an evening with strong winds      by heavy rain.

A. appeared     B. happened     C. accompanied    D. mixed