18. While we were having lunch, someone rang the bell.

19. The last time I went to dentist was 6 months ago.

20. She began studying Japanese 5 years ago.

21. After doing all his work, he went home.

22. After saving enough money, Steven bought a new motorbike.

23. When the guests had left, We tidied the house.

25. She noticed the boy run away from the house.

26. The policeman made the thief empty his pockets.

27. I heard him leave the house early this morning.