高考英语语法：原因状语从句的用法说明
原因状语从句主要的有because, as, since, seeing (that), now (that), considering (that) 等。如：
1. 由because引导
He couldn’t get to school because he had a cold. 他因患感冒而未能去上学。
I can’t take the examination because I am ill. 我不能参加考试因为我生病了。
He distrusted me because I was new. 他不信任我是因为我是新来的。
Because I worked fast, I finished early. 因为我干得快，所以我完成得早。
They can’t have gone out because the light’s on. 他们不可能出去了，因为灯还亮着。
He could not concentrate because the room was noisy. 他不能集中思想，因为房里太吵。
I read no further than the caption because the subject of the article seemed uninteresting. 我只看了标题，因为文章题目似乎不引人兴趣。
I could have gone with you because I was there at that time. 我本来可以和你一道去的，因为那时我也在那里。
2. 由as引导
As all the seats full I stood up. 因为所有座位都有人，我就站了起来。
As it’s raining, we’ll have to stay at home. 因为天下雨，我们得待在家里。
As all the seats were full he stood up. 由于所有座位都有人了，他站了起来。
We didn’t know what to do as we are not his parents. 我们不知怎么办好，因为我们不是他的父母。
3. 由since引导
Since everybody is here, let’s begin our discussion. 大家都到了，我们就开始吧。
Since we’ve no money, we can’t buy it. 因为我们没有钱，我们没法买它。
He could not answer the question, since he had not made up his mind. 他不能回答这个问题，因为他还没拿定注意。
4. 由seeing that引导
Seeing that it is 8 o’clock, we’ll wait no longer. 由于时间已到8点，我们将不再等了。
Seeing that it’s raining，we’d better stay indoors. 既然外边在下雨，我们待在室内。
Now that you are here, you’d better stay. 你既然来了，还是留下吧(既来之，则安之)。
5. 由now that引导
Now that you are here, you’d better stay. 你既然来了，还是留下吧。
Now that you’re well again. you can travel. 既然你身体好了，你现在可以旅行了。
Now that you mention it, I do remember the incident. 经你一提，我想起那事了。
注：其中的 that 通常可以省略。如：
Now (that) John’s arrived, we can begin. 既然约翰到了, 我 们可以开始了。