21.There have been several new events （项目）______to the program for the 2008 Beijing Olympic Game.
A. add B. to add C. adding D. added
22. By the time Jane gets home, her aunt ____for London
A. will leave B. leaves C. will have left D. left
23. You don’t know _____great effort I have made _____ him to stop smoking. Anyway, my effort has paid off.
A. What a ; to persuade(说服) B. What a ; persuade C. how ; to persuade
D. how a; to persuade
24._____with the problem of heavy traffic, more and more people prefer to take buses rather than drive cars.
A. Face B. Faced C. Facing D. To face
