I.      Passive voice:  Modal verb   Example: You should brush our teeth twice a day. ’ Our teeth should be brushed twice a day          1.      He might have caught the fish. ’................................................................................................................................................................. 2.      She could have washed the dress. ’................................................................................................................................................................. 3.      She is not going to pick many flowers. ’................................................................................................................................................................. 4.      Parents should give children a lot of love. ’................................................................................................................................................................. 5.      You must wash your hands. ’................................................................................................................................................................. 6.      He can speak four languages. ’................................................................................................................................................................. 7.      You must keep dogs outside shops. ’................................................................................................................................................................. 8.      Children should treat old men with respect. ’................................................................................................................................................................. 9.      My classmates used to call me John. ’ ................................................................................................................................................................ 10. He can’t repair my bike. ’ ................................................................................................................................................................ 11. I can buy this house. ’ ................................................................................................................................................................ 12. Sam ought to clean his room. ’ ................................................................................................................................................................ 13. We will shut the door. ’ ................................................................................................................................................................ 14. Nina shall call you as soon as she arrives. ’ ................................................................................................................................................................ 15. Sam can bring it back this morning. ’ ................................................................................................................................................................ 16. They will pass their exam. ’ ................................................................................................................................................................ 17. Henry ought to leave a message on the table for me. ’ ................................................................................................................................................................ 18. Vicky can pay her bill next week. ’ ................................................................................................................................................................ 19. You should clean the windows. ’ ................................................................................................................................................................ 20. You will phone me later. ’ ................................................................................................................................................................  

Để chuyển câu từ dạng Active sang dạng Passive voice với Modal verb, chúng ta cần thực hiện các bước sau:
1. Chuyển động từ (verb) sang dạng bị động bằng cách thêm "be" và chia động từ phù hợp với chủ từ mới.
2. Dời chủ từ của câu Active trở thành chủ từ của câu Passive và thêm "be" (nếu cần thiết).
3. Sau "be" là động từ 3 (past participle).

Sau khi áp dụng cách làm trên, chúng ta sẽ có các câu trả lời cho câu hỏi trên như sau:

1. The fish might have been caught by him.
2. The dress could have been washed by her.
3. Many flowers are not going to be picked by her.
4. Children should be given a lot of love by parents.
5. Your hands must be washed.
6. Four languages can be spoken by him.
7. Dogs must be kept outside shops by you.
8. Old men should be treated with respect by children.
9. I used to be called John by my classmates.
10. My bike can't be repaired by him.
11. This house can be bought by me.
12. Sam's room ought to be cleaned by him.
13. The door will be shut by us.
14. You shall be called by Nina as soon as she arrives.
15. It can be brought back this morning by Sam.
16. Their exam will be passed by them.
17. A message ought to be left on the table for me by Henry.
18. Her bill can be paid next week by Vicky.
19. The windows should be cleaned by you.
20. I will be phoned later by you.