16. They were working when the boss came in

17. When Carol got to the bus stop, the last bus had left 

18. I went to see the dentist after I had made an appointment

19. The workmen finished before the new owners had moved in

20. When the police arrived, the burglar had escaped

21. It was such a heavy rain that Laura walked to the office

22. By the time the police arrived, the robbers had gone away

23. I was having my breakfast when the phone rang

24. I took a taxi because I had missed the bus

25. When she came, I was having my dinner

26. When she was having her breakfast, the phone rang

27. When we arrived, David had gone home

28. After we had lunch, we went for a walk by the river

29. I began studying English 5 years ago

30. We last saw him in 2002

Chúc bạn học tốt ^_^ Nhớ vote cho mình 5 sao và cho mình trả lời hay nhất nhé =))

16. ⇒ They have worked when the boss came in.

17. ⇒ When Carol got to the bus stop, the last bus had already left.

18. ⇒ I went to see the dentist after having made an appointment.

19. ⇒ The workmen finished after the new owners having moved in.

20. ⇒ When the police arrived, the burglar had escaped.

21. ⇒ It was raining heavily, but Laura walked to the offce.

22. ⇒ By the time the police arrived, the robbers had gotten away.

23. ⇒ I was having breakfast when a phone rang.

24. ⇒ I took a taxi because I had missed the bus.

25. ⇒ When 

26. ⇒ When I was cooking my dinner, the phone rang.

27. ⇒ When we arrived, David had gone home.

28. ⇒ After having went for a walk by the river, we had lunch.

29. ⇒ I began studying English 5 years ago.

30. ⇒ We last saw him was when 2002.