21. The bill has to be paid.

22. For the time being, that group is being taught by Alice.

23. The report has to be finished.

24. Five suspects have been arrested by the police.

25. The little boy was bitten by the mad dog.

26. Our exercises are corrected by the teacher.

27. The accident was seen by Mr.Smith

28. A dancing class was started last week.

29. The package should be insured.

30. The bill may be paid for us.