because
单词辨析：
语气最强，表示因果关系，通常用来回答由 why 引导的疑问句。由 because 引导的分句置于句首时，须用逗号与主句隔开，置于句末时则不用隔开。
Because the traffic is so busy, she failed to arrive at the station on time.
因为路上交通太拥挤，她没能准时赶到车站。
He came back late because there was something wrong with his car.
他回来晚了，因为汽车出了故障。
如果所述理由是明显的或者已知的，则用 as 较 because 更为合适。
As it's raining, you'd better stay at home.
既然在下雨，你最好呆在家里。
He puts the ice cream into the fridge immediately, as it melts easily.
他马上把冰激凌放进冰箱，因为它很容易化掉。
for 属于并列连词，由它引导的分句表示补充说明性的理由，通常只能置于句末，且必须用逗号与前面的分句隔开。
He must have passed this way, for here are his footprints.
他肯定是从这条路走过去的，这里有他的脚印。
He has to work hard, for he wants to support his family.
因为要养家糊口，他必须努力工作。
当所述原因是已知的客观事实或被当作推断的理由时用 since，语气略强于 as。
Since he is absent, let's begin.
既然他不在，我们就开始吧。
Susan must have come back home, since her coat is not in the wardrobe.
苏珊肯定回过家，因为她挂在衣橱里的外套不见了。
相关例句：
I denied my father because I wanted to become someone else.
我和父亲断绝了关系，因为我想成为一个不一样的自己。
I don't get lonely now because I make the effort to see people.
我现在不觉得孤独了，因为我尝试着与人交往。
There's no chance that he'll surface because he's bound to have heard by now
他不会再出现了，因为他现在肯定听说了。
It is mainly because of my fault.
这主要是由于我的过错。
Just because something has always been done a certain way does not make it right.
仅仅因为老是以某种方式做事并不意味着这么做就是对的。
Maybe they just didn't want to ask too many questions, because they rented us a room without even asking to see our papers
也许他们只是懒得问太多的问题，因为他们都没要求看我们的证件就把一个房间租给我们了。