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