21. In ancient China, people used to send smoke _____ to warn that the enemy were coming.

    A. signs            B. signals        C. symbols          D. marks

答案:   B

解析:   这个题考四个名词的比较, 其中: signs 迹象; signals 信号;   symbols 象征;   marks 分数.

22. The icy conditions made our travel dangerous. So _____ going by car we took the underground.

    A. instead of                         B. in addition to

    C. as well as                         D. at the cost of

答案:   A

解析:   instead of 代替,而不是;     in addition to 除了…之外(还有);    as well as 也(除…之外), 既…又…;    at the cost of 以…为代价. 这道题横线后面是动名词形式,所以选项C和D首先排除.

23. Sometimes my job is boring, but _____ I enjoy it.

    A. by contrast                        B. by nature

    C. on the whole                       D. on the average

答案:   C

解析:   by contrast 与…相比,后面要跟with, by contrast with与…相比较;   by nature 本性,生性;    on the whole 总的来说;   on the average 平均.

24. I’ll buy the clock _____ it costs.

    A. what         B. whatever           C. where          D. however

答案:   B

解析:   不管花多少钱,我都买下这个钟.

25. _____ Mr.Wilson is well again, he can travel.

    A. Now that      B. So far             C. Though         D. Even if

答案:   A

解析:   Now that 既然; So far和现在完成时态连用.