28.The house was used (　　　 )a classroom in summer.

27.His mother was ill,and the doctor was operating (　　　 )her.

26. According (　　 ) his opinion,we should keep healthy (　　 )doing morning exercises.

25. Bamboo is used (　　 )making paper.

24.Please put(　　　 )a map on the wall.

22.The basket is filled (　　　 )eggs.

you work (　　　　 )this math problem?

21.When I was (　　 )trouble,it was he who helped me (　　　 ).

20.My situation is similar (　　　 )yours.

19. The girl takes (　　　　 )her father,not her mother.

18.If you think (　　 )a good idea,please call me right away.