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.

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.

53. out of question, out of the question

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

54. a second, the second

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

55. by day, by the day

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

56. the people, a people

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

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.

58. that, this

　that指代上文所提到的，this导出下文所要说的 I was ill. That's why…

59. none, nothing, no one

　none强调有多少，nothing, no one强调有没有，nothing指物，no one指人

　--- How many…/How much…? --- None.

60. anyone, any one

　anyone指人，不能接of，any one指人物均可，可接of any one of you