61. 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