61. on the average (=on average， on an average) 平均
62. (be) aware of (=be conscious of ， having knowledge or consciousness)意識(shí)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) 臥病不起。
65. at one's back(=supporting or favoring sb.) 支持，維護(hù); have sb. at one 's back 有…支持， 有…作后臺(tái)
66. turn one's back on sb. (=turn away from sb. in an impolite way) 不理睬(某人)，背棄，拋棄
67. behind one's back 背著某人(說壞話)
68. be based on upon 基于
69. on the basis of 根據(jù)…， 在…基礎(chǔ)上
70. beat…at 在…運(yùn)動(dòng)項(xiàng)目上打贏