2016届高考英语基础知识讲解与训练：连词_高考复习指南

2016届高考英语基础知识讲解与训练：连词

　　because, since, as引导原因状语时注意使用上的区别. 如果原因构成句子的最主要部分,一般用because ,因此because引导的从句往往放在句末。用why提问的句子，一定用because回答。如：He had to stay at home yesterday because he was ill.；如原因已为人们所知，或不如句子的其他部分重要，就用as，或 since。since比as更正式些。as和since引导的从句一般放在句子的开头。如：As you are tired, you had better rest./ Since everyone is here, now let's begin.

　　although和though引导让步状语从句往往用法一样，但注意以下区别 although用于各种文体，而though则多用于非正式的口语或书面语中。注意由although, though引导的从句后，主句不能用but，但可用副词yet, still。如：Although/ Though it rained all the morning, they still went on working.（或yet they went on working） though常与even连用，even though表示强调，意为"即使"，但不能说even although，例如：Even though I didn't understand a word, I ept smiling. ③though可用作副词，意为"然而"，常用逗号与句子分开。although则不能这样使用，它只作连词。例如：It was a quiet party, I had a good time, though.

　　当while, when, as引导时间状语从句时的区别 while引导的状语从句中动词必须是持续性。谓语动词多为进行时，或状态动词的一般时。while 的这些用法可用when代替，等于 "at the time that", "during the time that"。如：Please keep quiet while (when) others are studying； when除可指一段时间外，还可用来指一点时间，等于 "at the time"，也就是说when引出的时间状语从句中的谓语动词可以是终止性的，也可以延续性的。因此主句和从句的谓语可以是一般时进行时或完成时。如：When I went into the room, he was writing an article.（when不能换成while）He often makes mistakes when he is learning Chinese“gongfu”.（when可换成while） as常可与when，while通用，但强调"一边、一边"。例如：As (when, while) I was walking down the street, I noticed a police car in front of number 37. when引导的状语从句中的主语与主句主语一致，主、谓是"主语+系动词"结构时，这时主语和系动词可以省略。例如：When (he was) young, he worked for a rich man./ She'll be here to give you help when (if it is) necessary. when有时代替if，引导条件句，意为"如果"、"假如"，例如：I'll come when (if) I'm free.