单项填空
21. When you finish reading the book, you will have ________ better understanding of ______ life.
A. a; / B. the; a C. /; the D. a; the
22. He'll come _______ I promise him to buy that new dictionary.
A. so long B. on condition that C. as soon as D. by the time
23. 一 Herry! National Day is coming… 一 ? Just occupy yourself in your study．
A. How come B. Why not C. What for D. So what
24. To my surprise, my good friend _________ stay up to study to prepare for the next important exams organized by ten famous high schools.
A. should B. may C. must
