把下列语句变为被动语态：1.You should do your homework,now.2.They can fin

/>Your homework should be done now.(这个严格来讲不能用被动语态,因为意思变了)

The task can be finsihed by them in time.

3.The kids should be allowed  to do homework with their friends by parents.

4.The bike may not be put there.

5.Three units have been taught to us.
再问： 那 He has already pasted the letter. 怎么改？