21. What ____wonderful world it would be if all countries in tile world could live in____ peace with one another.

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

22. -- Isn't it hard to drive downtown to work'?

    -- Yes, that's why I __ to work by train.

    A. have gone                B. have been going   C. was going      D. will have gone