第一节：单项填空(共15小题；每小题1分，满分15分)
21—Don’t you think that island nations have advantages over other countries?
—______.
A. Yes. I agree with you. B. No. I believe that you’ve got it right.
C. Yes. I don’t think so. D. No. I think so.
22.------ Let’s try to solve this problem ________.
------ Ok. Then we needn’t worry about it any more.
A. after all B. at one time C. once and for all D. once in a while
