单项填空（共12分，每小题1分）
从下面各题所给的A、 B、 C 、D四个选项中，选择可以填入空白处的最佳选项。
21. My father is a doctor. ______works in a hospital.
He B. His C. Him D. Himself
解析：选A.考察人称代词。动前主格，动后宾格。因为有“works”,所以动前主格，答案选A。
22. Thanksgiving is always ______ the fourth Thursday in November.
in B. on C. at D. for
解析：选B.考察时间介词。At 用于点钟前；In 用于上下晚，年月季前；on用于具体时间前，而题干中出现了 “the fourth Thursday in November.”具体时间，答案选B。
23. - _______ you come to my party tonight?
- Sorry, I can’t. I have to do my homework.
Can B. May C. Must D. Should
解析：选A.考察情态动词。因为答语是“sorry， I can’t” ,根据问什么，打什么原则，答案选A
