18. Although I tried to stop smoking, it was very difficult to do.

19. This popular TV program is watched by millions of people every week.

20. Unless you have  a visa, you can't visit Thailand.

21. I asked Tam is she wanted to visit the Great Wall in China.

22. You didn't forget to buy me a newspaper, did you?

23. I prefer reading books to going to the cinema.

24. My parents haven't gone to HN since 2003.

25. The teacher told the boy not to write on the board.

26. I have never listened to jazz music before.

27. My grandfather used to tell us fairy stories when we were small.

28. If you try your best, you will be successful.

18. Although I try to stop smoking, It was very hard to do. 

19 This popular TV program is watched by millions of people every week. 

20. Unless you have a visa you can't visit Thaidland.

21. I asked Tam if she wanted to visit the Great Wall in China.

22. You didn't remember to buy me a newspaper, did you?

23. I prefer readinf books to going to the cinema. 

24. My parents haven't gone to Hanoi since 2003.

25 The teacher told the boy not to write on the board. 

26. I have never listened to jazz music before. 

27. My grandfather used to tell us fairy stories when we were small.

28. If you try your best You will be successful.