21. You needn't do all the homework.              chuyển thành câu bị động
……all the homewwork need to be done 
22. You ought to tell him early.
………he ought to be told early 
23. They don't use the room very often.
……………the room isn't used very often
24. They must widen the road to school this year.
…………the road to school is widen this year 
25. Have you done your homework?
…………has your homework been done
26. Did you finish your work early?
………was your work finished early
27. She has to pick fruit very early in the morning.
……………fruit has to be picked early in the morning
28. The house was dirty because she hadn’t cleaned it for weeks.
………the house hadn't been cleaned for weeks
29. She is taking care of the baby girl.
…………the baby girl is being taken care of by her 
30. Children should treat old men with respect.
……………old men should be treated with respect by children
31. She was wearing her new T-shirt when I met her yesterday.
……………her new t shirt was being worn when i met her yesterday 
32. The waiter brings me this dish.
………this dish is brought to me 
33. Our friends send these postcards to us.
…………these postcards are sent to us 
34. Their grandmother told them this story when they visited her last week.
…………this story was told by their grandmother when they visted her last week 
35. Tim ordered this train ticket for his mother.
…………this train ticker was ordered for tim's mother 
36. You didn’t show me the special cameras.
…………the special cameras wasn't showed to me 
37. She showed her ticket to the airline agent.
…………her ticker was showed to the airline agent 
38. He lends his friend his new shoes.
…………his new shoes are lent to his friend
39. She left her relatives five million pounds.
………five million pounds were left for her relatives 
40. The shop assistant handed these boxes to the customer.
……………these boxes was handed to the customer