2008高考英语专题复习 连词 ppt.pptVIP

* because,for, since, as 的区别： because语气强，表示客观必然原因： He is absent, because he is ill. for语气轻，表示非客观必然的原因，是主观可改变结果的原因，甚至是猜测可能的原因： He is absent, for he is busy. He must be ill, for he is absent. since,as 都是不讲自明的原因，是已知的原因： Since I am a boy, let me carry the case. As you don’t fell well, you had better stay at home. When,while,as 引导时间状语的区别： 1、When可指时间点，又可指时间段，从句中可用延续性动词，也可用非延续性动词。 When I got home, he was having supper. When I was young，I liked dancing． 2、While总是指一个时间段，从句中必须用延续性动词。 While I slept， a thief broke in. Don′t talk so loud while others are working. 3、as 表示两个动作同时发生：一个主语同时进行两个动作：一种状态随另一种状态的变化而变化。表示当……时一面……一面，随着。从句中多用表示动作的动词，而不用be动词或表示感觉、理解、知道这类动词。 As he stood there, he saw two men enter the bar.She dropped the glass as she stood up.The students took notes as they listened.As it grew darker it became colder. 注意：①when从句与主句动作先后发生时，不能与while，as互换。如：When he has finished his work，he takes a short rest． (when = after)When I got to the cinema，the film had already begun. (when = before) ???? ②when从句动词为终止性动词时不能由while替换。如：??When he came yesterday，we were playing basketball． 说明：此时when也不能用as替换，因为as从句为终止性动词时，主句通常也必须是终止性动词。 ③当从句的谓语是表动作的延续性动词，when, while和as才有可能互相替代。如：????While／When／As we were still laughing, the teacher came in. 正当我们仍在大声嘻笑时，老师进来了。 ④从句表示随时间推移连词能用as，不用when 或while。　As the day went on, the weather got worse.　　　　日子一天天过去，天气越变越坏。 ⑤当从句的谓语是终止性动词，而且主句的谓语也是终止性动词时，when可和as通用，而且用as比用when在时间上更为紧凑，有“正当这时”的含义。如：He came just as (或 when) I reached the door. 。⑥从句的谓语动词如表示状态时，通常用while。如：We must strike while the iron is hot. 。 ⑦When ,while 的其他用法： 1.We were having supper when the telephone began to ring. 2.Why use metal when you can use plastic. 3.I like playing football while he likes tennis. 4. While I admit his good points, I can see his shortcoming. 5.　While he loves his students, he is very strict with them whether 与 if 均为 “是否” 的意思。但在下列情况下，whether 不能被 if 所取代： 1.whether 引导主语从句（包括从句在句首的位置）应当用whether，不用if，如： Whether it is true remains a problem. W