其实as有两种意思一个是，因为，而另一个是，当就是说，as可是当作because,也能当成是whenfather step in as i'm doing homeworkfather step in when i'm doing homework当我在做功课时，爸爸进来了。i cannot go home as it's raining nowi cannot go home because it's raining now我不能回家，因为现在正在下雨。所以，as和because两者都能换着来用。要是说该用哪个，就要看你自己的语感了。
