18b increasing

19b have 

20b saw

III.21b was painting

22c she

23d doesn't he

24c while

25c didn't

IV.26b tell

27c excited

28b until

29c because

30a pronouncing

V.31 it is said that they bought this shop last year

They are said to have bought this shop last year. 

32 he asked me how much I thought it would cost

33 mr.brown whose team has lost the game looks very sad

 34 You know the man who sat next to me at Nam's birthday party last night, didn't you?

35. Minh spends 2 hours doing his homework every day.

36. Because it rained heavily, we were late for school

37. We used to be made to clean the house by my mother

38. She said she was working in a restaurant, and didn't care much for it

39. I haven't spoken to her for 2 years

40. It is interesting to go swimming in the river in the summer