31, comfortable

32, swimming

33, well

34, different

35, unhealthy

36, illness

37, collection

38, explanation

39, B→tall

40, A→saying

41, B→rang

42, C→their

43, C→do

44, B→were performed

45, B→helping

46, C→came and gave

47, The sister asked Tom if he was hungry

48, The little has put a lot of effort in the work

49, When did you study medicine?

50.John wasn't strong enough to go to school

51, Peter is taller than Tom

52, pollution

53, ill

54, laws

55, smoke

56, lung

57, Leads

58, health

59, it

60, climate

61, floods

B.

31.comfortable

32.swimming

33.well

34.different

35.unhealthy(a trong bài phải chuyển thành an nữa nhé)

36.illness

37.collection

38.explanation

C.

39.A->are growing

40.A->saying(after+V-ing)

41.B->rang

42.B->himself

43.C->do

44.B->were performed

45.B->helping

46.C->came and gave

D

47.The sister asked Tom if he was hungry.

48.The little has put a lot of effort in the work.

49.When did you study medicine?

50.John wasn't strong enough to go to school.

51.Peter is taller than Tom.

E.

52.pollution

53.ill

54.laws

55.smoke

56.lung

57.Lead

58.health

59.it

60.climate

61.floods