在每次的SAT考试中，语法部分对于逻辑主语判断的考察几乎会占到三分之一，这着实是一个不小的比例。虽然这部分大多题目类型比较浅显易懂，有些甚至一步可以找出答案，但是考官如果换个出题思路，不加以提示，考生就会陷入其套。因此这里要告诉大家的是警惕SAT语法中的逻辑主语问题。为了帮助SAT考生迅速理解这个问题并掌握解决办法，下面小编就为大家整理了解析SAT语法中的逻辑主语问题。
一、逻辑主语问题的常见形式有下列几种：
1. 句子以现在分词开始
例如，Lacking good instruction, my mistakes in creating a graph to illustrate historical trends were numerous.( 句子以现在分词lacking开始)
my mistakes in creating a graph to illustrate historical trends were numerous
I made numerous mistakes in creating a graph to illustrate historical trends
there were numerous mistakes in the graph I created to illustrate historical trends
I created a graph to illustrate historical trends with numerous mistakes
The graph I made for illustrating historical trends had numerous mistakes
2. 句子以过去分词开始
例如，Carried by the strong, dry winds of the stratosphere, the 1980 eruption of Mount Saint Helens caused dust thatcrossed the United States in three days and circled the globe in two weeks. (句子以过去分词carried开始)
the 1980 eruption of Mount Saint Helens caused dust that
Mount Saint Helens’ eruption in 1980 caused dust that
dust from the 1980 eruption of Mount Saint Helens
dust from the 1980 eruption of Mount Saint Helens that
there was dust from the 1980 eruption of Mount Saint Helens and it
3. 句子以介词加分词开始
例如，By simply entering an internet website or calling a toll-free number, a catalog order can be placedfor almost anything from cheesecakes to fully equipped desktop computers. (句子以介词by加分词enteringor calling开始)
a catalog order can be placed
by placing a catalog order
they will place your catalog order
you can place a catalog order
your catalog order can be placed
4. 句子以连词加分词或形容词开始
例如，While driving down the road, the house with the large yard and small pond attracted the family’s attention. (句子以连词while加分词driving down开始)
the house with the large yard and small pond attracted the family’s attention
the house having the large yard and a small pond attracted the attention of the family
the house with the yard and small pond was attractive to the family’s attention
the family’s attention was attracted by the house with the large yard and small pond
the family was attracted to the house with the large yard and small pond
二、修改方法
从语法上而言，如果句子开始是分词结构，那么它的逻辑主语必须是整个句子的主语。在修改句子题中，却往往相反，即句子的主语不是分词结构的逻辑主语。修改的方法是“一步必杀”法：将句子的主语替换为分词结构的逻辑主语(一般藏在句子中)。正确答案通常就是以分词结构的逻辑主语为句子主语的选项。根据“一步必杀”法，上述句子修改如下。
1. Lacking good instruction, my mistakes in creating a graph to illustrate historical trends were numerous.
my mistakes in creating a graph to illustrate historical trends were numerous
I made numerous mistakes in creating a graph to illustrate historical trends
there were numerous mistakes in the graph I created to illustrate historical trends
I created a graph to illustrate historical trends with numerous mistakes
The graph I made for illustrating historical trends had numerous mistakes
现在分词lacking的逻辑主语，即整个句子的主语应该是“I”，而实际上却是“my mistakes”。修改时只需要将句子的主语改为“I”就可以了。符合这个要求的有与两个选项，其中选项将numerous mistakes放错了位置，使得整个句子意思荒谬。因此为正确答案。这也告诉考生，正确答案只要改正原句的主要错误就可以了，而无须做太多额外的修改，因为与原句相比，这么做将使改后的句子变得面目全非。
2. Carried by the strong, dry winds of the stratosphere, the 1980 eruption of Mount Saint Helens caused dust thatcrossed the United States in three days and circled the globe in two weeks. (句子以过去分词carried开始)
the 1980 eruption of Mount Saint Helens caused dust that
Mount Saint Helens’ eruption in 1980 caused dust that
dust from the 1980 eruption of Mount Saint Helens
dust from the 1980 eruption of Mount Saint Helens that
there was dust from the 1980 eruption of Mount Saint Helens and it
过去分词carried的逻辑主语，即整个句子的主语应该是“dust”(dust 被winds吹走)，而实际上却是“eruption”。修改时只需要将句子的主语改为“dust”就可以了。符合这个要求的有与两个选项，其中选项保留了原句的that，使得that之后的crossed成了that引导的从句的谓语，也使得整个句子没有谓语，因此为干扰选项， 为正确答案。
3. By simply entering an internet website or calling a toll-free number, a catalog order can be placedfor almost anything from cheesecakes to fully equipped desktop computers. (句子以介词by加分词enteringor calling开始)
a catalog order can be placed
by placing a catalog order
they will place your catalog order
you can place a catalog order
your catalog order can be placed
介词by之后的现在分词entering与calling的逻辑主语，即整个句子的主语应该是人，例如you、one等，而实际上却是“a catalog order”。修改时只需要将句子的主语改为人就可以了。符合这个要求的有与两个选项，其中选项存在代词混用的情况(they与your无法协调) ，因此为干扰选项， 为正确答案。
4. While driving down the road, the house with the large yard and small pond attracted the family’s attention. (句子以连词while加分词driving down开始)
the house with the large yard and small pond attracted the family’s attention
the house having the large yard and a small pond attracted the attention of the family
the house with the yard and small pond was attractive to the family’s attention
the family’s attention was attracted by the house with the large yard and small pond
the family was attracted to the house with the large yard and small pond
连词while之后的现在分词driving down的逻辑主语，即整个句子的主语应该是人，也就是句中的family，而实际上却是“the house”。修改时只需要将句子的主语改为family就可以了。符合这个要求的只有选项，因此 为正确答案。选项 的主语是attention，而不是family，因此是干扰选项 。
另外我们我们来看道较为典型的题目(2010,10/S 10, 3)， 希望这些实例分析可以让大家明白。
Recalling how difficult it is to park a car at the airport, our decision was taking the train.
1.Our decision was taking the train
2. Our decision was to take the train
3. We decided to take the train
4. Taking the train is what we decided to do
5. It was our decision to take the train
根据这道题目的非谓语recalling, 我们得知做这个动作(回忆，想起)的主语必定是人，所以一步可以得知答案是C,主语确定为WE,我们。
但是同学们在考试或平时的训练中却存在一些问题，出题者一旦把句式稍作变化，同学们就不知所措，出现错误。例如：
1.句式颠倒莫困惑
Tomato soup appeals to all age groups and can be made particularly delicious if adding sweet red peppers. (2011.1/S 10, 6)
(A) delicious if adding
(B) delicious by the addition of
(C) delicious, adding
(D) delicious, add
(E) delicious, by the addition of
不用说，同学们应该看出病句D,E, 而C存在逻辑主语错误。而总有同学提出疑问，为什么A选项也是错误的呢?原文如果翻译为“番茄汤如果加上甜甜的胡椒粉会诱惑到所有人，而且特别好吃。”， 看似非常流畅，为什么就出错了呢?这里很多同学在考试的时候都是受到中式思维(Chinglish)的影响。其实很多时候，虽然中文的翻译读上去挺通畅的，但是大家容易忽略其英语语法的有效性和严谨程度，而这一点也正是SAT语法特别强调的。
在此题中如果选A, If adding 的施动者为前面提到的tomato soup, 试问番茄汤又岂能自己去加上胡椒粉呢?因此if adding 用法违背了逻辑主语的判断，正确答案应为B(by the addition of )。 在这里，考官只是把我们常看到的非谓语动作放在了主要句子的后面，而并非常见的句型(-ing, SVO)， 但性质没有变过，同学须注意。
2. 从句中见真功夫
The agency reports that by rigorously enforcing state regulations, industrial pollution has been successfully reduced to acceptable levels. (2010.1/S10, 14)
(A) industrial pollution has been successfully reduced to acceptable levels
(B) acceptable levels of industrial pollution have been successfully reduced
(C) a reduction of industrial pollution to acceptable levels has succeeded
(D) they have succeeded to reduce industrial pollution to acceptable levels
(E) it has succeeded in reducing industrial pollution to acceptable levels
在that之前，主句部分已经结束，由that带起从句，而从句中有一个by doing 形式的结构(by enforcing state regulations), 做enforce这个动作的主语只可能是人或者组织，工业污染或其减少都不可能自己实施规章制度，因此答案锁定在D和E. 再细看之前主句的主语为agency, 单数，因此答案选择E(it 指代agency.) 此处也是提醒同学切勿觉得翻译顺畅就没头脑地选择了A选项!
有意思的是，在2012年10月的考题中出现了类似的题目：
Our tour guide requested that, while hiking through the national park, our garbage not be thrown on the trails.
(A) our garbage not be thrown
(B) our garbage should not be thrown
(C) not to throw our garbage
(D) we did not throw our garbage
(E)we not throw our garbage
这也是2012年10月考试中IS题中出得最好的一题。有同学可能根据“抓句子主干”而忽略了插入语，很容易选B 但是此次的插入语中有重要句型即非谓语hiking(和刚才一题的by rigorously enforcing state regulations一样，ing形式出现在从句，不太显眼，容易被忽视)，所以从句中的逻辑主语必须是hiking动作的发出者，因此把答案锁定D,E 接下来根据request后面的搭配，sb. request/demand/require/suggest/advise that sb.(should) do…而且should 可以省略，所以是E。
通过以上大量实例分析，希望大家可以针对文中介绍的方法进行有针对性的备考，预祝大家在SAT考试中取得好成绩!
