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;