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

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

73. believe in (=have faith or trust in;consider sth./sb. to be true)  相信，依赖，信仰

74. benefit (from)  受益，得到好处

75. for the benefit of  为了…的利益(好处)

76. for the better  好转

77. get the better of (=defeat sb.)  打败，胜过

78. by birth  在出生上，论出身，按血统   at birth  在出生时   give birth to出生

79. blame sb. for sth. 因…责备某人   blame sth. on sb. 把…推在某人身上

80. in blossom开花(指树木)  be in blossom开花(强调状态)  come into blossom开花(强调动作)

81. on board  到船上，在船上，上火车或飞机

82. boast of(or about)  吹嘘

83. out of breath  喘不过气来

84. in brief (=in as few words as possible)  简言之

85. in bulk  成批地，不散装的

86. take the floor  起立发言

87. on business  出差办事

88. be busy with sth. 于某事  be busy doing sth. 忙于做某事

89. last but one  倒数第二

90. but for(=without)  要不是表示假设