逻辑主语问题是SAT语法部分的一个常见问题，对于句子修改题(Improving Sentences)而言更是如此。为了帮助SAT考生迅速理解这个问题并掌握解决办法，本文拟从它的常见形式与修改方法两个方面进行阐述。
一、常见形式
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)
(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
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 that crossed the United States in three days and circled the globe in two weeks. (句子以过去分词carried开始)
(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
3. 句子以介词加动名词开始
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加动名词entering…or calling…开始)
(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
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)
(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
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。英语作文
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