句子成分之——－状语的具体讲解（四）原因状语
导读：原因状语解释了主语的动作或者状态。
1. 介词短语做状语
2. 形容词做状语
3. 分词做状语
4. 状语从句（区分了 because, since, for, as的用法）
1. 介词短语做原因状语：
because of , due to, on the account of, owing to, as a result of 等词可以引导原因状语，后面需要接：名词（词组），代词，动名词。
（接名词）Newton discovered gravity due to an apple.
牛顿因为一个苹果发现了万有引力。
（接名词词组）He can’t forget the past because of the old days with his wife.
他忘不掉过去是因为忘不掉和他妻子一起度过的陈年往事。
（接代词）My mom disagreed with my decision. As a result of this, I changed my major. 我妈妈不同意我的决定。因此，我换了个专业。
（接动名词）On the account of loosing old friends, he can’t focus on the study.
由于失去了老朋友，他没办法再专注于学习。
because of , due to, on the account of, owing to 基本相同，可用在句首或者句尾，其中owing to在用在句尾的时候前面要加“逗号”，because of更倾向口语
Because of my bad leg ,I couldn’t walk so fast as the others.
由于我的腿坏了，我不能像其他人走得那么快。
Owing to his careless driving, we had a bad accident.
由于他驾驶疏忽,我们发生了次大车祸.
Your failure is due to negligence.你的失败是由于疏忽所造成的.
2. 形容词做原因状语
形容词做原因状语时，表示的是一种状态做原因。
Thirsty, he went to the teahouse for a drink first. 因为渴了，他先到茶社里去喝点水。
Afraid of being late, they came by taxi. 因为怕迟到，所以他们坐出租车来的。
3. 分词短语做原因状语
分词短语在句首时，经常表示原因状语
Not having got enough hands, we had difficulty in completing the work in time. 由于人手不够，我们很难按时完成任务。
Excited at the moment, she went to London alone. 由于心血来潮，她独自去了伦敦。
Sent back home, the old man got to calm down. 因为被送回了家，老人才慢慢平静了下来。
4. 从句作原因状语
引导原因状语从句的从属连词有because（因为）, as（由于）, since（既然）, now(that)（既然）, when（既然）, seeing (that) （由于，鉴于）, considering (that)（考虑到）, given (that) （考虑到）,for（为）等
（1）because引导的原因状语从句一般放于主句的后面，because从句位于句首时要用逗号分开，放在句末时，可不用逗号分开。because表示直接原因，语气最强，最适合回答why引导的疑问句。
例如：
I do it because I like it.
我做这件事是因为我喜欢。
You can trust those products because the quality never varies.
你可以信赖那些产品，因为它们的质量从来不变。
We went by bus because it was cheaper.
我们乘公交汽车去，因为这样便宜一些。
注意：“not ... because”结构中的not否定的是because引导的整个从句，例如：
误：The country is not strong because it is large.
正：The country is strong not just because it is large.
国强不在大。
I didn't help him,not because I was unwilling,but because I was unable to do it.
我没有帮助他，不是因为我不愿意，而是因为我力不从心。
2. since引导的原因状语从句一般放于主句之前表示已知的、显然的理由(通常被翻译成“既然”)，较为正式，语气比because弱。
例如：
Since you are free today, you had better help me with my mathematics.
既然今天你休息，你最好帮我补习数学。
Since you don't trust him,you should not employ him.
你既然不信任他，你就不该雇用他。
注意： seeing (that)， now (that)， considering (that)， in that这几个词汇与since引导的原因状语从句意思相近，都表示“既然”。
例如：
Seeing (that) he refused to help us, there’s no reason that we should now help him.
他既然曾经拒绝帮助我们，我们没有理由要来帮助他。
Now (that) you are grown up, you should not rely on your parents.
既然你长大了，就不应该依靠你的父母了。
Considering (that) everybody is here, let’s begin our discussion.
既然大家都到了，我们就开始讨论吧。
In that he is ill, he feels unable to do it.
因为他生病了，他觉得做不了那件事。
3. as 引导原因状语从句时表示附带说明的“双方已知的原因”，语气比since 弱，较为正式，位置较为灵活(常放于主句之前)。
例如：
As it is raining, you’d better take a taxi.
既然在下雨，你最好乘出租汽车。
As you are tired, you had better rest.
既然累了，你最好休息一下。
