27.Your trousers____ dirty.You must have____ washed.

A.is;il　 B.are;it　 C.are;them　 D.is;them

key: C 有人戏说裤子两条腿,所以是复数.有道理

26. The police ____ the murderer everywhere when he suddenly appeared

in a theatre.

A. is searching for　　　　　 B. were searching for

C. are searching for　　　　　 D. were searching

key: B 是警方的人,不是一个单位;search 为搜(身);search for=look for

25."All____ present and all____ going on well," our monitor said.

A.is;is　　 B.are;are　　 C.are;is　　 D.is;are

key: A 第一个all 指所有人;第二个all是情况

24.Many a man ____ come to help us.

A.have　　　 B.has　　　 C.is　　　 D.are

key: B　 这个把它背下来

23.Theis is one of the most interesting questions that ____ asked.

A.have　 B.has　　 C. have been　　 D.has been

key: C

22.He is the only one of the students who ____ elected.

A. are　　 B.have　　 C.has　　 D.is

key: D　 比较: He is one of the students who are elected.

21.The United States of America ____one of the most developed

　 countries in the world.

A.is B.are C.was D.were

key: A 主语是一个国家

20. The Olympic Games ____ held every ____ years.

A.is;four　 B.are;four　 C.is;five　 D.are;five

key: B

19. A chemical works____ built there.

A. is to being　 B.have been　 C. were to　 D.has been

key: D works 工厂　

18. Chairman Mao' s works ____ published.

A. has been　 B.have been　 C.was　 D.is

key: B works 著作,作品 毛主席选集已经出版了,当然是复数了.