综合类考试：常考从句解析之状语从句
状语从句指句子用作状语时，起副词作用的句子。它可以修饰谓语、非谓语动词、定语、状语或整个句子。根据其作用可分为时间、地点、原因、条件、目的、结果、让步、方式和比较等从句。状语从句一般由连词(从属连词)引导，也可以由词组引起。从句位于句首或句中时通常用逗号与主句隔开，位于句尾时可以不用逗号隔开。
现将状语从句的类别、用法、考点等归集如下，以帮忙职称英语考生对状语从句来重新熟悉并达到熟练运用，达到提高成绩的目的。
一、考点聚焦
1、时间状语从句(1)as、when、while用法as表示“当……的时候”，往往和when/ while通用，但它着重强调主句与从句的动作或事情同时或几乎同时发生。She came up as I was cooking.(同时)The runners started as the gun went off.(几乎同时)
when：(at or during the time that )既可以表示在某一点的时候，又可表示在某一段时间内，主句与从句的动作或事情可以同时发生也可以先后发生。It was raining when we arrived.(指时间点)When we were at school， we went to the library every day.(在一段时间内)
while意思是“当……的时候”或“在某一段时间里”。主句中的动作或事情在从句中的动作或事情的进展过程中发生，从句中的动词一般要用延续性动词。在when表示a period of time时，两者可以互换。Please don’t talk so loud while others are working.He fell asleep while/when reading. Strike while the iron is hot.(用as或when不可，这里的while意思是“趁……”)
(2)引导时间状语从句的连接词除上述外还有：①till， not … until …， until， before， sinceDon’t get off the bus until it has stopped.He waited for his father until(till)it was twelve o’clock.It will be five years before he returns from England.
②hardly / scarcely … when， no sooner … than， as soon as once表示“一……就”As soon as I have finished it ， I’ll give yu a call.Once you show any fear， he will attack you.We had hardly got / Hardly had we got into the country when itbegan to rain.No sooner had he arrived / He had no sooner arrived than she started complaining.
③directly， immediately， the moment， the minute that… 一……就He made for the door directly he heard the knock.
④each time， every time， by the timeEach time he came to my city， he would call on me.注意：表示未来情况，主句用将来时，从句用现在时。
2、让步状语从句(1)although与though可以引导让步状语从句，不能与but连用，但可以与yet连用。Although they are poor，(yet)they are warm-hearted.(2)even if或even though引导让步状语从句，表示“即使”，“纵然”，用来使人注意下文所强调内容的性质。I’ll get there even if(though)I have to sell my house to get enough money to go by air.(3)no matter后接上who、what、where、how等疑问词，也可以在这类疑问词后面加上ever构成whoever、whatever、wherever、however等。Don’t trust him， no matter what / whatever he says.Whoever breaks the law will be published.No matter how hard the work is， you’d better try to do it well.(4)as也可以引导让步状语从句。要用倒装。Child as(though)he is， he knows a lot.Much as I like it， I won’t buy.Try as he would， he couldn’t lift the heavy box.
3、原因状语从句：because， for， as， since， now that(1)表示不知道的原因时用because，即说话人认为听话人不知道，因此because从句是全句最重要的部分，通常它被置于主句之后。You want to know why I’m leaving？ I’m leaving because I’m full.for虽然表示不知道的原因，但其语气较because要弱得多，是可说可不说的话，它只能置于主句之后，这时，for是并列连词。如果不是因果关系，而是对前面主句的内容加以解释或推断时，只能用for.如：It’s morning now， for the birds are singing.(很显然，鸟叫不可能是“现在已是早上”的原因。)(2)表示已经知道的原因时用as或since，即某种原因在说话人看来已经很明显，或已为听话人所熟悉，因此它是句中不很重要的部分。since要比as正式一些，它们通常被置于语句之前，但有时却相反。Seeing all of the children already seated， he said，“Since everyone is here， let’s start.”(3)下列情况下只能使用because：①在回答why的问句时；②在用于强调句型时；③被not所否定时。
4、地点状语从句：where， whereverMake a mark wherever you have any questions.We will go where the Party directs us.
5、目的状语从句：that， so that， in order that注意：目的状语从句的谓语动词常与情态动词连用，否则可能是结果状语从句。不可置于句首。
6、结果状语从句：that， so that， so … that， such … that …注意：so 形容词/副词 that从句；such 名词 that从句。
7、方式状语从句：as， as if(though)I’ll do as I am told to.It looks as if it is going to rain.
8、比较状语从句：than， as
9、条件状语从句：if， unless， so (as) long as， in case， once， a far as， on condition that.注意if与unless的区别：不能用and连接两个unless从句，即不能有… unless …，and unless … 。但if … not and if … not却不受此限。You won’t lose your weight unless you eat less and unless you exercise more.(×)但可以说 … unless you eat less and exercise more.