57. it, one

　it同一物体，one同类不同一 I lost my pen. I have to buy a new one.

56. the people, a people

　the people指人，a people指民族 The Chinese is a peace-loving people.

55. by day, by the day

　by day白天，by the day按天计算 The workers are paid by the day.

54. a second, the second

　a second又一，再一，the second第…… He won the second prize.

53. out of question, out of the question

　out of question毫无疑问的，out of the question不可能的

52. on fire, on the fire

　on fire着火,on the fire在火上 Put the food on the fire. The house is on fire.

51. in class, in the class

　in class在课上，in the class在班级里 He is the best student in the class.

50. in charge of, in the charge of

　in charge of管理，负责照料， in the charge of由……照料 He is in charge of the matter. The matter is in the charge of her.

49. in bed, on the bed

　in bed卧在床上，on the bed在床上 The book is on the bed. He is ill in bed.

48. in office, in the office

　in office在职的，in the office在办公室里 He is in office, not out of office.