20.解析：前有since，主句则用完成时，因此处表示现在仍在进行改革，故用现在完成进行时。

答案：have been working

19.解析：用来指增长或减少的幅度。

答案：by

18.解析：上文有After a great wave of conversions。

答案：another

17.解析：in the 1990s，固定搭配。

答案：the

16.解析：此处­ing作定语，修饰countries，意为“领先的”。

答案：leading

5.Steve and Mark are both studying in the Chinese Department of China's Renmin University. They want to do some research on Chinese ancient literature.

答案：1-5　DBECA

4.Edward is a senior student in Beijing Foreign Language University. He likes traveling very much and has made up his mind to work as an interpreter for some joint­venture enterprises (合资企业).

3.Lora and Peter， visiting professors from Australia， are both crazy about Chinese traditional culture. At weekends they like to call on Chinese families to learn about Chinese festivals as well as their history.

2.Simon comes from Egypt. He is now studying in Beijing Art Academy. He shows great interest in Chinese ancient characters. Now he wants to know much about it.