将下列句子改为被动语态（跪求答案）

1.This kind of tractor is made by that factory.
2.A lot of tall buildings in the city have been put up by we in the last few years.
3.He laughed at by they.
4. The children were taken care well by they.
5. The exercise-books must be hand in tomorrow.
6.A doctor was sent for by them immediately
7.could it be finished in two hours
8.it may be done a little earlier
9.your bike must not be put here
10.he was never heard say"thank you"in his life
11.he was made to tell them everything
12.he was seen to come out of the room
13.a shirt was bought from she
14.a warm welcome was given to the foreign friends by the children
15.English is teached by Mr Smith
16.she was helped do her homework
17.a new railway being built by they
18.her nanme will be renmembered forever by the Chinese people
19. the child was found in the park finally
20. never has the name been heard of
21.all the money has been spent
22.the letter has not been sent yet
差不多就是这样了

1.this kind of tractor is made by that factory.
2.a lot of tall buildings have been put up by us in the city in the last few years.
3.he is laughed at by them.
4.the children were taken good care of by them
5.the exercise-books must be handed in tomorrow.
6.they were sent for a doctor immediately.
7.can it be finished in two hours
8.it may be done a little earlier
9.your bike must not be put here
10.he was never heard to say "thank you"in his life
11.him was made to tell them everything
12.him was seen come out of the room
13.a shirt was bought for me by her
14.the foreign friends were given a warm welcome by the children
15.English is taught by Mr Smith
16.she was helped to do her homework by me
17.a new railway is being built by them
18. her nanme will be remembered by the Chinese people forever
19.the child was finally found by them in the park
20.the name has been never heard of by us
21.all the money has been spent by them
22.the letter has not been sent by us yet