21. ____ she knew nothing about it.

       A. It looks that          B. It seems as if         C. It appears as if       D. It seems that

22. His suggestion is ____ worth ____.

       A. very; visiting                                        B. much; being visited                       

       C. well; to be visited                                  D. well; a visit

23. You can not imagine the difficulty they had ____ the problem. It isn’t ____ easy.

       A. to solve; so           B. solved; so             C. solving; that          D. solved; that