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　　原因状语从句

　　连接词：because，since，as，for，now that，in that，owing to，due to，thanks to，because of，as a result of;

　　比较：because，since，as和for

　　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。

　　He is absent today, because / for he is ill.

　　He must be ill, for he is absent today.

　　now that ：既然;

　　in that :因为，通常只能放在句中，强调重要的，唯一的的原因;

　　eg：Now that this semester is finished, I am going to rest a few days and take a trip.

　　Human beings are different from animals in that human can speak and think.

　　owing to, due to, thanks to, because of , as a result of等短语后面只能接词或短语，不能接从句。

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