初中重要短语及知识点总结3：原因状语从句

（三）原因状语从句知识点总结

　　是用来说明引起主句这个结果的原因的从句，在初中阶段引导原因状语从句的从属连词主要的有because, as, since, for等。例如：

　　1.I didn;t go to school yesterday because I was ill. 我昨天没去上学，因为我生病了。

　　2. Since everybody is here, let;s begin our meeting. 既然大家都来了， 让我们开始开会吧。

　　3. As you are in poor health, you should not stay up late. 既然你身体不好， 你就不该熬夜。

　　4.I asked her to stay to tea, for I had something to tell her. 我请她留下来喝茶，因为我有事要告诉她。

原因状语从句应注意的问题

　　1、because, since, as, for，辨析

　　1）because语势最强，用来说明人所不知的原因，回答why提出的问题。当原因是显而易见的或已为人们所知，就用as或 since.

　　I didn;t go, because I was afraid.

　　Since /As the weather is so bad, we have to delay our journey.

　　2）由because引导的从句如果放在句末，且前面有逗号，则可以用for来代替。但如果不是说明直接原因，而是多种情况加以推断，就只能用for.例：

　　He is absent today, becaus e / for he is ill. 　　He must be ill, for he is absent today.

　　3） as和for的区别：通常情况下，as引导的从句在主句前，for引导的从句在主句后。例:As the weather is cold, I stay at home.（同义句） I stay at home, for the weather is cold.

　　2、because习惯上不与so连用

　　汉语习惯上说“因为…所以…”，但英语习惯上却不能将 so与because 连用：

　　正：Because it was raining, we stayed at home. / It was raining, so we stayed at home.

　　误：Because it was raining, so we stayed at home. 因为下雨，所以我们呆在家里。

　　3、because 从句与 because of短语的转换

　　Because引导的原因状语从句有时可与because of 短语转换，because of后加的原因可以为好或坏 ，但最正规的还是because.

　　He can;t come because he is ill. / He can&;t come because of his illness. 他因病不能来。

　　I said nothing about it because his wife was there. / I said nothing about it because of his wife;s being there. 因为他妻子在那儿，我对此事只字未提。

　　常见考法

　　对于原因状语从句的考查，多以单选和完形填空的形式，从连词的意义角度让大家选择连词。

　　典型例题：He found it increasingly difficult to read, ____ his eyesight was beginning to fail.

　　A. and B. for C. but D. or

　　解析：his eyesight was beginning to fail&34;是;hefound it increasingly difficult to read&34;的原因，因此本题应选用可以表示原因的连词for引导原因状语从句。

　　答案： B

　　误区提醒

　　除了because、since 、as、for这四个词的辨析外，对于because 从句与 because of短语的区分也是难点之一。Because引导的原因状语从句有时可与because of 短语转换，because of后跟的是短语，because后跟的是句子。

　　典型例题：He didn&39;tgo to work the heavy rain.

　　A .because B.because of C.so D.since

　　解析：题干的意思是“由于那场大雨，他没有去上班”，the heavy rain.表示原因，排除C；since和because 表示原因，后面跟的是从句，也就是说必须是一个完整的句子，本题中the heavy rain没有主语和谓语。只是一个短语，所以排除A和C；because of表示“由于···”，后跟名词、代词或短语。

　　答案：B