21.   We have every reason to believe that ______ 2010 World Expo in Shanghai will be ____  success.

A. /; a             B. the; /            C. the; a        D. a; a

22. When I opened the door, I found my father sitting in his chair, completely _____in a magazine.

A. absorbed         B. gathered        C. losing         D. concentrated

23. “Tom graduated from college at a very young age.”

   “Oh, he ____ have been a very smart boy then.”

     A. could                B. should             C. might            D. must