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英语专业四级填空常考结构TOP12(11)

2009-06-30来源:

十一、状语从句省略结构

Metals expand when they are heated.    Metals expand 是主句;when they are heated 是状语从句。但是这个状语从句中可以省略掉they are, 句子变成:Metals expand when heated. 但是并不是所有的状语从句都可以这么省略。

这种省略从句主语的方式理论上需要满足以下两个条件:
    第一、从句主语和主句主语必须保持一致;    第二、从句的谓语必须是be动词,主语和be动词同进同出,比如上面的they和are要么同时省略,要么同时保留。

例1:Although___rigid, bones exhibit a degree of elasticity that enables the skeleton to withstand considerable impact.  (A) apparently    (B) are apparently    (C) apparently their    (D) are they apparently

分析:连词although通常引导主谓完整的状语从句,当从句主语与主句主语相同、从句谓语又为系表结构时,则可省略主语和连系动词,故正确答案为(A)。Although apparently rigid = Although bones are apparently rigid, 注意bones和are必须同时省略。

  因此,我们从上面的例题中来分析一下填空题中状语从句省略以后的形式:though, although, even thought, while, If, when等为引导状语从句的词;这些词后面一定+形容词(分词),主句(注意逗号的后面是主句,前面是从句)

例2:All marble is composed of crystals of the minerals calcite or dolomite, ___, are perfectly white.    
(A) when, pure which    (B) when, which pure    (C) which, pure when   (D) which, when pure

分析:空格前是个完整的句子,空格后是系表结构,空格处显然缺非限定性定语从句的引导词兼作从句主语。(A)、(B)不引导非限定性定语从句,可首先排除。(C)中的pure和when位置错了,故选(D)。注意when pure是插入语,同时也是省略用法when they are pure;which are perfectly white, 状语从句省略结构,

例3:___relatively costly, the diesel engine is highly efficient and needs servicing infrequently
(A) Even    (B) It is    (C) Even though    (D) There is

分析:B和D填入后,都是构成两个主句,不对;Even though则引导状语从句,even though it is, 这里it is 已经省略。