二、单项填空（本题有20小题；每小题0.5分，共10分）
在A、B、C、D四个选项中，选出可以填入空白处的最佳选项。
21. —Waiter, ______?
—Wait a minute, sir. That’s $ 80 altogether.
A. would you charge me B. how much did we eat
C. may I have the bill, please D. would you take the money
22. It is known that water is not ______ endless resource, nor ______ that can be made once more.
A. the; / B. an; one C. an; that D. /; one
23. ______ in the regulations that you should not tell others the password of your e-mail account.
A. It is required B. What requires C. What is required D. It requires
24. — Ann is in hospital.
— Oh, really? I ______ know. I ______ go and visit her.
A. didn’t; am going to B. don’t; would C. don’t; will D. didn’t; will
