Ｕｎｉｔｓ３－４重点句型解析

彭　英

1.unless引导条件状语从句

【课文原句】You should not go rafting unless you know how to swim，and you should always wear a life jacket.

【经典考例】We wont keep winning

games________we keep playing well.(NMET 2006 浙江卷 )

A.because B.unlessC.when D.while

【考点解析】句意“除非我们继续打好比赛，否则我们就不能连续获胜。” because意为“因为”，引导原因状语从句；unless意为“除非；如果不”，引导条件状语从句；when意为“当……时候”，引导时间状语从句；while表示“在……期间；虽然”，可引导时间、让步状语从句或并列句。答案为B。

2.as well as连接比较状语从句

【课文原句】Eco-travel is a way to find out what can be done to help animals and plants as well as people.

【经典考例】John plays football________ ，if not better than.David.

A.as well B.as well as

C.so well D.so well as

【考点解析】句意：“约翰如果踢足球不比大卫踢得更好，也至少与他踢得一样好。”as well as 在课本这个句子中是连词，意为“以及”，是个固定整体而在考例中的as well as 只有后一个as是连词，意为“像”，“同”，第一个as 是副词，意为“一样”，修饰well，所以不是一个固定整体。可以按句意不同而说 as bad as，as early as ，as clever as 等，不能混为一谈。考例中的as well as，意为“同……一样好”。题中的if not better than是插入语，省去后不难看出试题变成了同级比较结构“John plays football as well as David”。答案为B。

as well as作“以及”解用来连接两个并列的名词或代词。它强调的是前一项，后一项只是顺便提及，not only…but also侧重后者，也就是说A as well as B= not only B but also A。例如：

Mr.Brown has experience as well as knowledge.布朗先生不仅有知识而且有经验。(侧重前者，即experience)(=Mr Brown has not only knowledge but also experience.)(着重后者，即but also后面的部分)

as well as连接并列主语时，动词须和as well as前面的主语在数上取得一致；not only…but also连接句子中的并列成分时，动词的数则和but also后面的主语取得一致。例如：

The pilot as well as two of the passen-gers has escaped death.(as well as前的主语pilot是单数，故动词用has。)

Not only two of the passengers but also the pilot has escaped death.(but ɑlso后的主语the pilot是单数，故动词用has。)

3.before引导时间状语从句

【课文原句】However，before she could think twice，the water was upon her.

【经典考例】

—Why didnt you tell him about the meeting?

—He rushed out of the room________I could say a word.(NMET 2006 四川卷)

A.beforeB.until

C.whenD.after

【考点解析】句意“你为什么没告诉他这次会议的情况?”“我还没来得及说，他就从房间里冲了出去。”before引导时间状语从句，表示“在……之前；还没来得及”，强调从句动作发生之前，主句动作已发生。答案为A。

注意before其它的用法：

1.表示“在……之后……才”。

The American Civil War lasted four years________the North won in the end.(NMET 2005广东卷)

A.after B.before C.when D.then

【解析】：答案为B。本题考查连词before表示“在……之后才……”之的用法，根据本句含义“美国南北战争持续了四年，北方才最终取得胜利"，可知本题应选B。

2.表示“在……之前就……”。这时主句与before从句中的两个动作按时间先后依次发生。

It was evening________we reached the little town of Winchester.(NMET 2004天津卷)

A.that B.until C.since D.before

【解析】：答案为D。本题考查连词before表示“在……之前就……”的用法。句意是“我们到达小镇Winchester之前就已经是傍晚时分了”。

3.表示“趁……”，“等到……”，或 “没等……就…… ”等。

He made a mistake，but then he corrected the situation________it got worse.(NMET 2003北京卷)

A.until B.when C.before D.as

【解析】：答案为C。由made a mistake和转折词but可知本题句意是“他出了差错，但没等其进一步恶化，他就改正了”。故正确答案为C。

4.用于句型“It + will/would be + 时间段 + before...”句型中，表示“要过多久才…”，其否定形式“It will/would not be +时间段+ before…”表示“不久就……，过不了多久就……”。

The field research will take Joan and Paul about five months；it will be a long time________ we meet them again.(NMET 2007安徽卷)

A.after B.before C.since D.when

【解析】：答案为B。before 用于肯定的“It + will be + 时间段 + before...”句型中，表示“要过多久…才…”。

4.动词-ing形式作伴随状语

【课文原句】“Run!” Jeff shouted，seizing her arm.

【经典考例】“You cant catch me!”

Janet shouted，________away.(NMET 2005 全国卷II)

A.runB.running

C.to runD.ran

【考点解析】句意：“‘你抓不住我的!珍妮特边喊边跑。”由句中的逗号可知，shout后不是并列的谓语动词，而是表伴随的状语，由于run和主语Janet是主动关系，故用动词-ing形式。一般来说动词-ing形式作伴随状语，它所表达的动作或状态是伴随着句子谓语动词的动作而发生或存在的。答案为B。5.must have done表推测

【课文原句】Tree after tree went down，cut down by the water，which must have been three meters deep.

【经典考例】

—Tom is never late for work.Why is he________ absent today?

— Something________to him.________ (NMET 2005江西卷)

A.must happen

B.should have happened

C.could have happened

D.must have happened

【考点解析】句意“汤姆上班从不迟到。今天他为什么没来?”“他一定是出了什么事情。” 答案为D。must have done表对过去所发生事情 的肯定性推测，如果是否定性的推测，要用cant /couldnt have done。

注意对must have done进行反问疑问时，反意疑问句应为对过去发生的那个动作的时间提问，应特别注意句子中的时间状语。试比较：

You must have been to Beijing several times，havent you? 你肯定到北京去过好几次了，是吗?

Li Tao must have given up smoking three years ago，didnt he? 李涛一定是三年前戒了烟的，是吗?

Smith must have got to London by now，hasnt he? 史密斯现在肯定已经到了伦敦，是吗?★