无论是机考还是纸考SAT，都会对Writing文法进行考核，其中就有大量考察基础语法知识的题目，涉及到了很多知识点。今天我们来一起学习语法基础知识的一个常考知识点：逻辑主语一致。
逻辑主语是非谓语动词动作的执行者或承受者。SAT考试中，经常考察分词的逻辑主语和主句的主语要保持一致这个考点。分词包括现在分词和过去分词，例如“seeing”就是现在分词，而“seen”属于过去分词。它们有什么区别呢？现在分词（doing形式）表示主动的行为，而过去分词（done形式）表示被动，所以“seeing”这个动作的逻辑主语就是看东西的人/动物，而“seen”的逻辑主语是被看见的东西。
我们看下面这个例子：
Seen from the hill, _________.
A. I found the city pretty.
B. the city is pretty.
根据我们刚才说的，seen的逻辑主语是被看见的东西，所以这个句子主句的主语应该与之一致。可以看到：A选项的主语是I，能够主动做出“看”这个动作；B选项的主语是the city，只能“被看见”。所以这里应该填入的句子就是B. the city is pretty。
下面我们就来做几道题目练习一下，看看这个知识点究竟是如何考察的~
题目练习
Practice 1
In 2016, engineer Vanessa Galvez oversaw the installation of 164 bioswales, vegetated channels designed to absorb and divert stormwater, along the streets of Queens, New York. By reducing the runoff flowing into city sewers, _____.
Which choice completes the text so that it conforms to the conventions of Standard English?
A) the mitigation of both street flooding and the resulting pollution of nearby waterways has been achieved by bioswales.
B) the bioswales have mitigated both street flooding and the resulting pollution of nearby waterways.
C) the bioswales’ mitigation of both street flooding and the resulting pollution of nearby waterways has been achieved.
D) both street flooding and the resulting pollution of nearby waterways have been mitigated by bioswales.
首先，我们可以看到，ABCD四个选项语序不同，每个选项的主语也不同，所以这道题就是要考察逻辑主语一致这个考点。阅读文章发现，最后一个句子的主语应该和“reducing the runoff flowing into city sewers减少流入城市下水道的径流”的逻辑主语一致。
浏览四个选项，主语分别为:
A:“the mitigation缓解”
B:“the bioswales生态湿地”
C:“the bioswales’ mitigation生态湿地的缓解作用”
D:“street flooding and the resulting pollution街道浸水和由此产生的污染”
再通过原文“… bioswales, vegetated channels designed to absorb and divert stormwater”可知bioswales是为吸收和分流雨水而设计的植被通道，可以完成“reducing the runoff flowing into city sewers”这一工作，所以对应选择B选项。
Practice 2
African American Percy Julian was a scientist and entrepreneur whose work helped people around the world to see. Named in 1999 as one of the greatest achievements by a US chemist in the past hundred years, _____ led to the first mass-produced treatment for glaucoma.
Which choice completes the text so that it conforms to the conventions of Standard English?
A) Julian synthesized the alkaloid physostigmine in 1935; it
B) in 1935 Julian synthesized the alkaloid physostigmine, which
C) Julian’s 1935 synthesis of the alkaloid physostigmine
D) the alkaloid physostigmine was synthesized by Julian in 1935 and
同样，这道题最后一个句子的主语应该和“Named in 1999 as one of the greatest achievements by a US chemist in the past hundred years”的逻辑主语保持一致。“Named”表示被动，所以逻辑主语应该是一项被命名的achievement成就。
浏览四个选项，主语为：
A. Julian;
B. Julian;
C. synthesis合成;
D. the alkaloid physostigmine毒扁豆碱。
其中只有这种化学物质的合成才是科学家Julian的成就，所以这道题应该选择C选项。
文末福利
做完上面几道题，大家有没有掌握“逻辑主语一致”这个语法知识点呢？想要在SAT考试Writing部分获得高分，必须建立清晰的语法知识体系，了解每个语法点会如何考察，并配合练习进行强化，明确考点，快速解题。
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