13. College students were a major force in the campaign, although participants of all ages were involved.尽管参加这次运动的人涉及到各个年龄段的人，但是大学生是这场运动的主导力量。14. thir...
37. The custom can be traced back to the roman era.付小费这种习俗这种风俗可以追溯到古罗马时代。38. A more common belief is tips were first given in the 18th century England...
be free from没有……的，不受……影响be identified as…被认为是…be known as被称做……，以……著称be known to为……所熟知be popular with…受……欢迎be prepared for对……做好准备be regarded as被认为是…，被当...
take place发生，进行take the place of… 代替…make sense讲得通，有意义a great/good deal of大量(修饰不可数名词)influence on影响reply to…回答…，答复…once upon a time从前once in a while偶尔...
by all means无论如何，必定by means of… 借助于…，用…by no means决不by mistake错误地in nature本质上on occasion有时，不时in particular特别地，尤其，详细地in the first place起初，首先in the last...