1 doing
John is doing his homework in the classroom.
约翰正在做作业。
2 being done
The homework is being done by John.
约翰正在做作业
3 having done
After having done the homework,John left the classroom.
做完作业后，约翰离开了教室。
4 having been done
The homework having been done, John left the classroom.
写完作业后，约翰离开了教室。
祝你开心 满意记得采纳哦~
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