状语从句的语法点在高中英语语法中是比较重要的一块。在高考中也是常年必考项目，尤其是在选择题中。本期我们就着重介绍状语从句如何归纳复习。

　　状语从句的种类较多，可分为时间、地点、原因、目的、结果、条件、方式、比较、让步九种。下面详细介绍各种状语从句中需要的注意点。

　　时间状语从句

　　1.需注意各种从属连词，尤其是比较容易引起错误的搭配和不常使用的词。如：hardly … when，no sooner … than，the moment，once，each time等。

　　2.注意时态的呼应。

　　时间状语从句中用一般现在时态代替将来时态。此外，since引导的从句和主句时态不一致，hardly … when，no sooner … than时态的搭配都是需要引起注意的。

　　3.主句后跟until/till引导的句子时，要注意主句动词的延续性(见例1)和终止性(见例2)的区别，还要注意对until引导的内容进行强调的用法(见例3)。

　　例1.He slept until 8 in the morning.

　　例2.He did not get up until 8 in the morning.

　　例3.It was not 8 in the morning that he got up.

　　例4.Not until 8 did he get up.

　　4.注意While，when，as引导的时间状语从句的差别。

　　从句的谓语是短暂动词时，不能用while引导;as用于表示两个动作几乎同时进行，而且从句的动词不能是表示状态的动词(见例2);as之后不能用分词作状语;从句的谓语是持续性的时候，三者可以互换(见例1);when还可表示某事突然发生(见例3)，此外不能用其他的词代替。

　　例1.When/While/As he was in Australia, he learned to play the guitar.

　　例2.As the days went by, she knew more about her hometown.

　　例3.I was locking the door when the postman came.

　　例4.When/While waiting for his turn, she picked up a magazine and began browsing through it.

　　原因状语从句

　　主要区别because, as，since的用法。

　　because的语气最强烈，用于回答why引起的问题;since和as用于双方皆知的原因，一般放在句首，相对而言，since比as更正式一点;for引导的原因往往是一种补充说明，不用于句首，用逗号和前面的句子分开。

　　结果状语从句

　　as和such的用法是一个难点，归纳如下：

　　Such a/an + adj. + singular noun

　　Such + adj. + plural noun

　　Such + adj. + uncountable noun

　　So + adj. + a/an + singular noun

　　So + adj./adv.

　　So + many/much/little/few + noun

　　Such + little(小) + noun

　　目的状语从句

　　引导词有：in order that, so that, in case, for fear that等。从句中的谓语常和may, might, can, could, should, would连用。当主句和从句的主语一致时，可用in order to和so as to加不定式来代替从句。

　　条件状语从句

　　引导词除了常用的if, unless, as/so long as之外，还有on condition that, provided that, supposing, in case，if only。条件状语从句和时间状语从句一样，一般现在时表示将来时。尤其需要注意的是条件句可以是真实的或者虚拟的。如果是假设的条件，需要用虚拟语气，在用虚拟语气时，要特别注意错综条件和省略条件的句子以及虚拟条件和真实情况混杂的句子。如：

　　If you had taken his advice, there would be no trouble now.

　　But for the police, the wounded driver would have lost his life.

　　He would have lent you his new carat that time, but you are so careless driver.

　　方式状语从句

　　要注意由as if/though引导的从句虚拟和陈述语气的使用区别。

　　It seems as if the ship will leave the harbor in a minute.(陈述)

　　The cheats acted as if they had been working very hard the whole night.(虚拟)

　　让步状语从句

　　要注意以下几点：

　　1. though和although都不能和but连用。

　　2. although一般在句首，而though还可以作并列连词，(相当于and yet)放在两个分句之间用逗号分开。

　　She wanted to have another try, though she had no chance.

　　3.However, whatever, whoever, wherever, whenever等在状语从句中等同于no matter how/what/who/where/when, 但在名词性从句中不能等同。比较：

　　However difficult the task may be, we will finish it within the time given.

　　=No matter how difficult the task may be, we will finish it within the time given.

　　Whatever he says, I will not change my mind.

　　=No matter what he says, I will not change my mind.

　　Whatever he said in the court was written down by a secretary for later use.

　　≠No matter what he said in the court was written down by a secretary for later use.

　　比较状语从句

　　1.比较的对象要平衡一致。

　　Her handwriting is more beautiful than anybody else’s in her class.

　　2.从句中常常省略一些相同的成分。

　　My parents do not love pop music as much as I (do).

　　3.比较级常用表示程度的状语有：much, still, far, a lot, a great deal, three times, a bit,rather, slightly等。