81. at, in (表地点)

　　at小地点，in大地点 arrive at a small village, arrive in Shanghai

　　82. increase to, increase by

　　increase to增长到…，increase by增长了… The number increased by 2,000 to 5,000.

　　83. since, for (完成时间状语)

　　since接点时间或一句话，for接一段时间 for three years, since 3:00

　　84. on earth, on the earth, in the earth

　　on earth在世上，在人间，到底，究竟，一点也不，on the earth在地上，在地球上，in the earth在地下，在泥土里 no use on earth

　　85. in surprise, to one's surprise

　　in surprise惊奇地，to one's surprise使某人吃惊的是，

　　86. in the air, on the air, in the sky

　　in the air正在酝酿中，on the air播送，广播，in the sky在天空中 His show is on the air at 6:00 tonight.

　　87. through, across

　　through穿越空间，across在…上穿过 through the forest, across the desert

　　88. on the way, in the way

　　on the way在前往…的路上，in the way挡路 The chair is in the way.

　　89. above, on, over

　　above在上面，不接触，on在上面，接触，over在正上方 fly over the hill

　　90. until, not…until

　　until到…为止， not…until直到…才(常跟点动词连用)I waited until 3:00. He didn't come until 3:00.

　　91. besides, except, except for

　　besides除了…还(包括在内)except除了(不包括在内)，except for整体…除了某一点以外 The composition is good except for a few spelling mistakes.

　　92. whether, if

　　当是否解时，只有在宾语从句中二者可以互换，其余都用whether，当如果解时用if I don't know if/whether he will come. If he comes, I'll let you know.

　　93. because, since, as, for

　　原因由强到弱为：because, since/as, for. 在句中的位置如下：1)…because… 2) Since/as…, … 3) …, for… Since I was ill, I didn't go.

　　94. when, as, while (表时间)

　　when从句动词点动词，持续性动词均可，as重在表示动作同时发生，伴随进行，while从句动词为持续性动词 While I slept, a thief broke in.

　　95. the same…as, the same…that

　　the same…as和…一样的(相似但不同一)， the same…that 同一物体 This is the same pen that I used yesterday. (同一支笔)

　　96. as well, as well as

　　as well也，常放于句末，和and连用表示既…又;as well as并列连词，不但…而且… He is a professor, and a writer as well.

　　97. such…as, such…that

　　such…as像…样的，such…that如此…以至于 He is not such a fool as he looks like. He is such a good student that all the teachers like him.

　　99. because, because of

　　because连词，连接两句话，because of介词短语，后接词或短语 He didn't go to school because of his illness.

　　100. in order that, in order to

　　表目的，in order that后接句子，in order to后接动词原形 I got up early in order to catch the first bus. I got up early so that I could catch the first bus.