将下一句子改为被动语态（九年级英语）,能改几句就改几句,高手来

将下一句子改为被动语态（九年级英语）,能改几句就改几句,高手来
1.Who bought the book?
2.We saw him sitting there without doing anything
3.I will ring Tom up
4.Someone has taken the stranger to another hospital
5.Did he do his homework last night?
6.The students listened to the teacher carefully
7.He asked to play the piano last Sunday

各位不要误人子弟
第七句是 He was asked to play the piano last sunday
其余都对了 楼主相信我
1By whom is the book bought?（who is the book bought by?）
2He was seen by us sitting there without doing anything.
3Tom will be rung up by me.
4The strange has been taken to another hospital by someone.
5Was his homework done by him last night?
6The teacher was listened by the students carefully.