个并列谓语。主句用了一般过去时，从句也要用相应的过去时态；又因从句主语是knives，故填were。

　　15．Listening to loud music at rock concerts __has__ (have)caused hearing loss in some teenagers.

　　解析：句意：在摇滚音乐中，听嘈杂的音乐使一些青少年造成听力损失。本题考查主谓一致。动名词短语作主语时，谓语用单数。

　　Ⅱ.单句改错

　　1．Every girl and every boy have the right take part in the competition.(have→has)

　　2．Either she or you is to replace him to attend the meeting.(is→are)

　　3．Neither she nor I are wrong.(are→am)

　　4．Many a scientist have devoted their lives to science.(have→has)

　　5．The disabled is looked after well in our country.(is→are)

　　6．Tom is the only one of the students who are from abroad.(are→is)

　　7．Half of the work are left unfinished.(are→is)

　　8．A pair of new shoes were bought yesterday.(were→was)

　　9．Half of the apples has already been given to the children.(has→have)

　　10．Her trousers is of high quality indeed.(is→are)

　　Ⅲ.用括号内单词的适当形式填空

　　1．The teacher and writer __is__ (be) my friend.

　　2．Another three years __has__ (have) passed.

　　3．In front of the house __stand__ (stand)two apple trees.

　　4．A basketball team __has__ (have)5 members.

　　The basketball team __are__ (be)having baths now.

　　5．To learn one or two foreign languages __is__ (be)very important nowadays.

　　6．This kind of apple __tastes__ (taste)good.Apples of this kind taste(taste) good.

　　7．No one except his own supporters __agrees__ (agree)with him.

8．There __stands__ (stand) in the park a big tree about thirty feet