4．Catherine is the only one of the visitors who __knows__ (know)a little Chinese and is one of my net friends who __are__ (be) studying in China now.

　　解析：当one of前有the only修饰时，后面的定语从句的谓语动词用单数形式，否则用复数。

　　5．The police __are__ (be)keeping an eye on the suspect.

　　解析：考查主谓一致。句意：警察正在监视这个嫌疑犯。police是一个表示复数概念的名词，作主语时谓语动词用复数。类似的名词还有cattle，people等。

　　6．Every means __is used to__ (use)prevent the river from__being polluted__ (pollute).

　　解析：句意：每一种方式都被用来阻止河流被污染。be used to do sth.被用来做某事；prevent sth.from...阻止某事发生。every决定了谓语为单数；pollute与the river之间为被动关系。

　　7．When and where we will have our holiday __has__ (have) not been decided yet.

　　解析：考查主谓一致。句意：我们何时何地度假还没定。表示"到目前为止还没有决定下来"应用现在完成时；when and where作主语表示同一概念，谓语动词用单数。

　　8．Her family as well as she __are__ (be) glad to meet you here.

　　解析：考查主谓一致。as well as连接并列主语时，谓语动词的单复数与as well as短语之前的名词的单复数一致。集合名词在强调成员时，谓语动词用复数形式。

　　9．The number of tourists travelling abroad __is__ (be)rising gradually.

　　解析：考查主谓一致。句意：到国外旅游的游客的数目在逐渐上升。the number of...作主语时，谓语动词要用单数。

　　10．The restaurant with thirty waiters __is offered__ (offer)to him as a gift.

解析：句意：有30名服务员的饭店被作为礼物送给了他。主语后面若跟wit