SAT语法题目中的常见错误类型是逻辑主语错误，即句子的主语不是分词结构的逻辑主语。修改这种错误的方法很简单，只要用隐藏在句子中的逻辑主语替换掉句子原来的主语即可。我们通过以下四道例题来具体讲解这种方法：
1. Lacking good instruction, my mistakes in creating a graph to illustrate historical trends were numerous.
(A) my mistakes in creating a graph to illustrate historical trends were numerous
(B) I made numerous mistakes in creating a graph to illustrate historical trends
(C) there were numerous mistakes in the graph I created to illustrate historical trends
(D) I created a graph to illustrate historical trends with numerous mistakes
(E) 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，而原句中却是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(B)与(D)两个选项，其中(D)选项将numerous mistakes放错了位置，使得整个句子意思荒谬。因此(B)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，否则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 that crossed the United States in three days and circled the globe in two weeks.
(A) the 1980 eruption of Mount Saint Helens caused dust that
(B) Mount Saint Helens' eruption in 1980 caused dust that
(C) dust from the 1980 eruption of Mount Saint Helens
(D) dust from the 1980 eruption of Mount Saint Helens that
(E) 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)，而原句却是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(C)与(D)两个选项，其中(D)选项保留了原句的that，使得that之后的crossed成为that引导的从句的谓语，也使得整个句子没有谓语，因此(D)为干扰选项，(C)为正确答案。
3. By simply entering an internet website or calling a toll-free number, a catalog order can be placed for almost anything from cheesecakes to fully equipped desktop computers.
(A) a catalog order can be placed
(B) by placing a catalog order
(C) they will place your catalog order
(D) you can place a catalog order
(E) 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，而原句中却是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(C)与(D)两个选项，其中(C)选项存在代词混用的情况(they与your无法协调)，因此(C)为干扰选项，(D)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.
(A) the house with the large yard and small pond attracted the family’s attention
(B) the house having the large yard and a small pond attracted the attention of the family
(C) the house with the yard and small pond was attractive to the family’s attention
(D) the family’s attention was attracted by the house with the large yard and small pond
(E) 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，而原句中却是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(E)选项，因此 (E)为正确答案。(D)选项的主语是attention，而不是family，因此是干扰选项 。
由此可见，SAT语法部分的错误通常都是有规律可循的。只要能迅速将错误归类，并了解此类错误的一般改正方法，大多数SAT语法改错题就迎刃而解了。
