21. All the homework needn't be done. 

22. Him ought to be told early. 

23. The room isn't used very often. 

24. The road to school must be windend this year. 

25. Has your homework been done? 

26. Was your work finished early? 

27. Fruit has to be picked very early by her in the morning. 

28. The house was dirty becuase it hadn't been cleaned for weeks. 

29. The baby girl is being taken care of by her. 

30. Old men should be treated with respect by childrens.

21. You needn't do all the homework.

→ All the homework needn't be done. 

22. You ought to tell him early.

→ Him ought to be told early. 

23. They don't use the room very often.

→ The room isn't used very often. 

24. They must widen the road to school this year

→ The road to school must be windend this year. 

25. Have you done your homework? 

→ Has your homework been done? 

26. Did you finish your work early?

→ Was your work finished early? 

27. She has to pick fruit very early in the morning.

→ Fruit has to be picked very early by her in the morning. 

28. The house was dirty because she hadn’t cleaned it for weeks.

→ The house was dirty becuase it hadn't been cleaned for weeks. 

29. She is taking care of the baby girl.

→ The baby girl is being taken care of by her. 

30. Children should treat old men with respect.

→ Old men should be treated with respect by childrens.