第二部分 英语知识运用（共两节，满分45分）
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。
21. I bought third alarm clock in case other two fail to go off.
A. /; the B. a; a C. the; a D. a; the
22. Generally my father is a mild man, but when he gets angry, he _______ be fierce.
A. can B. should C. must D. shall
23. —Mr. Black becomes more and more forgetful.
