大学英语：重要词汇on the average(=on average，on an average)平均

62.(be)aware of(=be conscious of，having knowledge or consciousness)意识到，知道

63.at the back of(=behind)在…后面

64.in the back of 在…后部(里面);on the back of 在…后部(外面);be on one's back(=be ill in bed)卧病不起.

65.at one's back(=supporting or favoring sb.)支持，维护;have sb. at one's back 有…支持，有…作后台

66.turn one's back on sb.(=turn away from sb. in an impolite way)不理睬(某人)，背弃，抛弃

67.behind one's back 背着某人(说坏话)

68.be based on upon 基于

69.on the basis of 根据…，在…基础上

70.beat…at 在…运动项目上打赢

71.begin with 以…开始;to begin with(=first of all)首先，第一(经常用于开始语)

72.on behalf of(=as the representative of)以…名义