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连词比较

　　1) 并列结构中，or通常用于否定句，and用于肯定句。

　　2) 但有时and 也可用于否定句。请注意其不同特点：

　　There is no air or water in the moon.

　　There is no air and no water on the moon.

　　在否定中并列结构用or 连接，但含有两个否定词的句子实际被看作是肯定结构，因此要用and。

　　典型例题

　　---I don't like chicken ___ fish.

　　---I don't like chicken, ___ I like fish very much.

　　A. and; and　 B. and; but　C. or; but　D. or;and

　　答案C。否定句中表并列用or, but 表转折。

　　判断改错：

　　(错) We will die without air and water.

　　(错) We can't live without air or water.

　　(对) We will die without air or water.

　　(对) We can't live without air and water.

　　3 )表示选择的并列结构

　　(1) or　意思为"否则"。

　　I must work hard, or I'll fail in the exam.

　　(2) either…or　意思为"或者……或者……"。注意谓语动词采用就近原则。

　　Either you or I am right.

　　判断改错：

　　(错) They sat down and talk about something.

　　(错) They started to dance and sang.

　　(错) I saw two men sitting behind and whisper there.

　　(对) They sat down and talked about something.

　　(对) They started to dance and sing.

　　(对)I saw two men sitting behind and whispering there.

　　解析：

　　第一句： and 连接两个并列的谓语，所以 talk 应改为 talked。

　　第二句：and 连接两个并列的动词不定式，第二个不定式往往省略to，因此sang 应改为 sing。

　　第三句：and 连接感观动词saw 后面的用作的宾补的两个并列分词结构，因此whisper应改为whispering。

　　注意：and 还可以和祈使句或名词词组连用表示条件。(or也有此用法)

　　Make up your mind, and you'll get the chance.

　　= If you make up your mind, you'll get the chance.

　　One more effort, and you'll succeed.

　　= If you make one more effort, you'll succeed.

　　Some people love cats, while others hate them.

　　典型例题

　　--- Would you like to come to dinner tonight?

　　--- I'd like to, ___ I'm too busy.

　　A. and　 B. so　 C. as　 D. but

　　答案D。but与前面形成转折，符合语意。而表并列的and，结果的so，原因的as都不符合句意。

　　He hurt his leg, so he couldn't play in the game.

　　注意：

　　a. 两个并列连词不能连用，但therefore, then, yet.可以和并列连词连用。

　　You can watch TV, and or you can go to bed.

　　He hurt his leg, and so / and therefore he couldn't play in the game.

　　b. although… yet…，但although不与 but连用。

　　(错)　Although he was weak, but he tried his best to do the work..

　　(对)　Although he was weak, yet he tried his best to do the work.

　　其规律由so与such的不同词性决定。such 是形容词，修饰名词或名词词组，so是副词，只能修饰形容词或副

　　词。so 还可与表示数量的形容词many，few，much， little连用，形成固定搭配。

　　so + adj.　　　　　　　　　such + a(n) + n.

　　so + adj. + a(n) + n.　　　such + n. (pl.)

　　so + adj. + n. (pl.)　　　 such +n. (pl.)

　　so + adj. + n. [不可数]　　such +n. [不可数]

　　so foolish　　　　　　　　 such a fool

　　so nice a flower　　　　　 such a nice flower

　　so many/ few flowers　　　 such nice flowers

　　so much/little money.　　　such rapid progress

　　so many people　　　　　　 such a lot of people

　　so many 已成固定搭配，a lot of 虽相当于 many，但 a lot of 为名词性的，只能用such搭配。

　　so…that与such…that之间的转换既为 so与such之间的转换。

　　Eg :The MP3 cost me ________ money that I ccouldn't afford to buy it .

　　A .so much .B .such much C .so many

　　D . such many .(Key :A )

　　注意:too .... to .. ,so ..... that .... , such .... that .... , enough ..... to ...., 的互换.

　　so that to = in order to /that 的用法.

　　Eg A .He is too young to go to school.

　　B .He is ____ a young boy _____ he ____ go to school .

　　C .He is ____ young ____ he ____ go to school .

　　D .He isn't ______ _______ ______ go to school (Keys :B :such , that , can't C :so ,that ,can't .D : old ,enough to )　　

　　①关于not…until

　　He stayed there until it was very late.

　　句中，stay是可延续性动词，所以不用not。

　　He didn't leave until it was very late.

　　句中，leave是不可延续性动词，所以用not

　　②because, so;although, but

　　上面已经提到，because和so及although和but不连用。

　　例如:

　　Because he was late, he didn't catch the first bus.

　　一定不可以说

　　Because he was late, so he didn't catch the first bus.

　　③or还是and

　　祈使句+or+陈述句前后是对立的

　　祈使句+and+陈述句前后是统一的

　　(or或and后的陈述句，常用一般将来时)

　　Study hard, or you won't pass the exam.

　　Study hard, and you will pass the exam.

　　两句都可以转换成“If条件句+主句”形式，注意：要去掉or和and：

　　If you don't study hard, you won't pass the exam.

　　If you study hard, you will pass the exam.

　　④because, since, as, for表示原因时的区别

　　尽管because, for, since, as都表示原因，但是用法上有不同.

　　because通常表示说话人认为这种理由或者原因是听话人所不知道的.

　　如:

　　He didn't attend the meeting because he had too much work to do.

　　since表示的原因是人们已知的事实，常译作“既然”。

　　如：

　　Since he can't answer this question, you'd better ask someone else.

　　as表示原因与since差别不大，只是语气更弱,多译为“由于”

　　如：

　　As I haven't seen the film, I can't tell you what I think of it.

　　for表示因果关系时，只能放在主句之后，不能放在句首。而且经常是对主句补充说明理由或推断原因。

　　如：

　　It rained last night, for the ground is wet.

　　⑤ as, when, while

　　这三个连词都可引导时间状语从句，但用法有所不同。

　　1) 当某事正在进行的时候，又发生了另一件事。While, when, as 都可用来引导表示“背景”的时间状语从句。例如：

　　As/When/While I was walking down the street I noticed a police car.

　　2) 当两个长动作同时进行的时候，最常用的是while。例如：

　　While mother was cooking lunch, I was doing my homework.

　　3) 当两个动作都表示发展变化的情况时，最常用的是as。例如：

　　As children get older, they become more and more interested in things around them.

　　4) 当两个短动作同时发生时，或表示“一边…一边…”时，最常用as。例如：

　　Just as he caught the fly, he gave a loud cry.

　　She looked behind from time to time as she went

　　5) 当从句的动作先于主句的动作时，通常用when。例如：

　　When he finished his work, he took a short rest.

　　6) 当从句是瞬间动作，主句是延续性动作时，通常用when。例如：

　　When John arrived I was cooking lunch.

　　(6)if, whether

　　if和whether都可作“是否”讲，在引导宾与从句是一般可互换。例如：

　　I wonder whether (if) you still study in that school.

　　I don’t know whether (if) he likes that film.

　　1) 引导主语从句时。例如：

　　Whether he will come to the party is unknown.

　　2) 引导表语从句时。例如：

　　The question is whether I can pass the exam.

　　3) 在不定式前。例如：

　　I haven’t made up my mind whether to go there or not.