21. Although tea drinking is a considerable custom in the Far East, this custom first

      A                           B                     C

reached Europe for the first time during the 17th century.

                       D

答案：　Ｄ

解析：　去掉for the first time；　时间状语重复应用，注意前面的this custom first…。

22. The reason he has made such great progress in English is because he has never

        A                  B                      C           D

wasted his time.

答案： D

解析： Because 改为 that，这是一个宾语从句。

23. The dentist said that if my tooth went worse I should have to have it pull out.

　　　　　　　　　　　　　　　　　　　A    B          C                   D

答案： D

解析： pull改为pulled；have sth done 使…被…，表示这件事儿是让别人去做的，故动词用过去分词形式，表被动。

24. I object to war not because it ruins the economics¹ but that it seems inhuman².

            A          B                                  C         D

答案： C

解析： but that 改为 but because；注意与前面一句的关系.

25. The matter that you were arguing about last night has settled.

                A        B         C                      D

答案： D

解析： has settled 改为 has been settled.