2.as和since引导的原因状语从句

(1)as和since在引导原因状语从句时，意义差别不大，由这类从属连词引导的句子均侧重主句的内容，其原因只是附带原因。由since表示的原因通常指人们已知的事实，相当于汉语“既然”;由as表示的原因语气最弱，常见诸于日常对话，相当于汉语“由于”。

Since everybody is here，let's begin our discussion．

既然大家都到了，我们就开始吧。

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。

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．

我们不知该怎么办才好，因为我们不是他的父母。

提示：

如果从句所表示的原因还不是确定的事实，就不要用since，通常用because。

Did he come because he wanted to see his old friend?

他是不是因为要见老朋友才来的?

(2)as引导原因状语从句引起的倒装。

as在引导原因状语从句时，可以采用倒装语序。这时常常采用下面两种形式:

①“表语或状语+as+主语+谓语动词”。

The house was very quite，isolated as it was on the side of a mountain．

这幢房子由于孤零零地位于山腰，显得非常宁静。

Tired as they were，they went to bed as soon as they came back．

由于他们很疲劳，所以一回家就上床睡觉了。

Michael，fool as he was，completely ruined the dinner．

迈克傻乎乎的，把这次宴会完全给搅乱了。

Countrymen as they were，they regarded the mist but as an added obscuration，and ignored its humid quality．(《英语结构词》第970页，山东大学出版社，1987年)

因为是乡村居民，他们觉得起雾不过增加一点阴暗罢了，并不理会雾是潮湿的。

提示：

在这种句型中如果表语是单数可数名词，须用零冠词。

Coward as he was，he ran back as soon as the enemy attacked．

他是个胆小鬼，敌人一进攻，他就往回跑。

×A coward as he was，he ran back as soon as the enemy attacked．

但是在其前加上like时，又须用不定冠词:

Like a coward as he was，he ran back as soon as the enemy attacked．

Like a plucky small man as he was，he didn't mean to give in．(《英语结构词》第971页，山东大学出版社，1987年)

他是一个有胆量的人，并不打算屈服。

但是“like+名词+as．．”这一结构如果用在句子后面，那就只起解释的作用，意为“竟然那么做，真是……”，原因的意义变得很不明显。

She fought against it，like a brave woman as she was．(张鑫友，《英语语法难题探微词典》第570页，华中师范大学出版社》

她挺身而出，真是个勇敢的女杰。

Hard as he studied，he passed the test with ease．

由于他学习用功，所以他很轻松地通过了测试。

提示：

as在引导让步状语从句时也使用倒装语序。(见让步状语从句)至于何时表示“虽然”，何时表示“由于”，要根据上下文的意义来确定。

Old as he was，he ran forward at the signal to attack．

虽然他老了，但是他一听到冲锋号就往前冲。

Hard as he studied，he failed the test．

虽然他学习用功，但是还是没有通过测试。

②“现在分词+as+主语+do/did/does+句子的附加成分”或“过去分词+ as+主语+be动词的限定形式”。

I feel it to be a rare occasion，occurring as it does only once in many years．

我认为这种事情是罕见的，许多年才发生一次。

Knowing him as I do，I can tell you that he will not break his promise．

我很了解他，我敢跟你们担保他是不会食言的。

Written as it was in haste，the book was full of mistakes．

因为写得仓促，这本书错误百出。

Born as he was in this beautiful town，he hates to leave it．

出生于这个美丽的小镇，他不愿离开它。

提示：

上述结构中的as是为了强调前面分词的意义而插入的。如果去掉as从句，原句的意义没有改变，虽然as从句表达了原因意义。

Living(as we do)in a lonely village，we rarely have visitors．

(由于)我们生活在一个人迹罕至的村子里，很少有人来光顾。Diagnosed(as he was)with cancer，he was in low spirits．

(由于)被诊断出得了癌症，他情绪低落。