21. Air p                 is quite harmful to our health.

22. It's everyone's duty to protect(保护) our e                 from being polluted.

23. Most people in the world love p                , they don't need war(战争).

24. My family live in a big a                 in a big city.

25. Don't play football on the road. It's very d                .

26. You shouldn't b                 everything he says because he's not always honest.

27. You're right, so no one here d                 with you.

28. It's i                 for him to carry the heavy bag, because he is only two years old.

29. I p                 go there, but I don't decide.

30. We'll take part in all kinds of activities d                 the coming holidays.

31. If there were more trees on the earth, there would be less p                .

32. Don't throw litters away. We should protect our e                .

33. I hope everyone in the world can live with each other in p                .

34. He lives in an a                 with his parents.

35. Don't be near the lions. They are d                .

36. I b                 I can make progress if I do my best.

37. I agreed to have a picnic in the park on Sunday, but Lily d                .

38. He got up so early. It is i                 that he should have missed the train.

39. The news was p                (most likely) true.

40. Gina lives in her aunt's house d                 the weekend.

41. There are                 (大概) ten apples in the basket over there.

42. I think it's                 (可能的) for people to live in space one day.

43.