题目内容：

将下列句子改为被动语态.We must water the flowers. People cut down a lot of trees every year.
He cleaned his bedroom just now.
The teacher won't open the window.
Mary has forgotten the book.

优质解答

1、The flowers must be watered by us .2、A lot of trees are cut down by people every year .3、His bedroom was cleaned by him just now.4、The window won't be opened by the teacher.5、The book has been ...