21. He isn't old enough to get a driver's l                .

22. The drivers should pay more attention to the s                 of the children.

23. Terrible things are a                 things.

24. May I have my own c                 of the food and drink?

25. Parents should e                 their children to behave well.

26. My family was poor in the past. I had no c                 to go to college.

27. Can you l                 these books up and put them on the shelf?

28. You should always knock at the door before you e                 a room.

29. Unless you get a driver's l                , you can't drive a car.

30. There isn't any danger here. You are in s                 now.

31. We should always keep an eye on school                 (安全).

32. He had quite an                 (糟糕的) day yesterday.

33. In the modern                 (社会), cars are becoming more and more important.

34. We should                 (教育) children not to play with fire.

35. We offer free technical                 (支持) for those buying our products.

36. Peter's dream is to                 (进入) a medical college in the future.

37. Going to Hainan Island for the vocation will be a good                 (选择).

38. If you get a                 (机会) to go there, please take it.

39. When an earthquake happens, we should run to                 (安全) as quickly as possible.

40. Last night he had a(n)                 (可怕的) dream, and he couldn't sleep well all the night.

41. 婴儿在喝牛奶之前，牛奶应该加热。