By the time the teacher came, we had finished cleaning the classroom.
老师来的时候，我们已经打扫完教室了。
He thanks them for cleaning the classroom for him.
他感谢他们为他打扫教室。
They aren't cleaning the classroom.
他们没在打扫教室。
They didn't go back home until they finished cleaning their classroom.
他们直到打扫完教室后才回的家。
Our classroom needs cleaning. = Our classroom needs to be cleaned.
我们的教室需要打扫了。
We have finished cleaning the classroom.
我已经打扫完教室了。
教室需要（被）打扫。
Mike can't be cleaning the classroom.
Mike肯定不在打扫教室。
Mike can't be cleaning the classroom.
Mike肯定不在打扫教室。
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