线话英语语法讲堂：原因状语从句

　　
比较：because, since, as跟for CopyRight .com

　　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。当起因是不问可知的或已为人们所知，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，则可能用for来代替。但假如不是说明直接起因，而是多种情况加以推断，就只能用for。
He is absent today,英语学习网站, because / for he is ill.
He must be ill, for he is absent today. CopyRight .com

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