He must have finished the job yesterday怎么改为被动语态?

题目

He must have finished the job yesterday怎么改为被动语态?
还有几个也需要改1.He studies English with hismother at home,
2.He saw the bird flying in the sky.
3.He saw the bird fly in the sky.
都要改为被动

答案

The job must have been finished by him yesterday.1.English is studied by him with his mother at home.2.The bird was seen flying in the sky by him.3.The bird was seen to fly in the sky by him.就是这样...