70. letter of recommendation 信;letter of reference 信
71. look on the bright sides of things 看事物的光明面
72. no kidding 不是开玩笑吧
73. on the tip of one's tongue 就在舌尖
A: Are you sure you can’t remember the name of that record?
B: It’s just on the tip of my tongue!
74. quitting time 下课时间
I’m glad it’s almost quitting time.
75. take it over 重修
Don failed physics and had to take it over.
76. than necessary 比应该的要冷
The lab was cooler than necessary.
77. That’s easer said than done. 说来容易做来难
78. There is nothing to it. 没什么，很容易
I can run this projector. There’s really nothing to it.
79. with flying colors 成功
A: How did Ellen do on her American History exam?
B: She passed with flying colors.
80. You can bet your life 当然
A: Will Prof. Smith come to class on time?
B: You can bet your life.