23. The class is unusual _______ the students are all over fifty and none of them attended the middle school when they were young.

A. in how　　　 B. in what　　　 　　　　　　 C. in which　　 　　 D. in that

22. Dr. Frank failed many times but he finally 　　　　　 　to find a successful way to solve the problem.

A. broke off　　　　　 B. broke up　　　　　 C. broke down　　　　　　　 D. broke through

第一节：单项填空(共15小题；每小题1分，满分15分)

从A、B、C、D四个选项中，选出可以填入空白处的最佳选项，并在答题卡上将该项涂黑。

21.The bird ______ its wings and flew to the south.

A. beat　　　 B. hit　　 C. strike　　 D. struck