引导语：本文为小编为大家带来的语法解析之悬垂结构，希望对所有关注新SAT亚太首考动向的同学们有帮助。
新SAT考试中沿用了部分老SAT的语法考核点，其中modifier placement(修饰语)中悬垂结构的语病是很大的一个难点，尤其是涉及到None-finite verbs 非谓语动词部分，是SAT考试最常考到的内容。要避免悬垂结构的语病，首先要明确，作伴随状语的非谓语动词或介词短语实际上可以理解为省略了和句子主干相同的主语，如果逻辑上的主语和实际的主语不一致句子就会变得词不达意。分清楚伴随状语的逻辑主语，确保其和句子的主语保持一致是关键。下面我们来具体分析。
首先，非谓语动词包括现在分词(doing)，过去分词(done)，以及不定式(to do)三种形式。现在分词doing一般表示动作伴随着句子谓语的动作发生，和主语是主动关系;过去分词done表示和主语的被动关系;而不定式to do一般表示目的性质。
如何避免悬垂结构的出现呢?就是要保证none-finite verbs的主语和句子主语一致，具体我们看下面的例子：
Visiting Paris two hundred years ago, the city would have looked very different.
A) NO CHANGE
B) Paris would have looked very different.
C) the difference in the city would be seen.
D) you would have seen a very different city.
这个句子中，Visiting Paris two hundred years ago是主干部分的伴随状语，visiting的动作应当是由人发出，去拜访两百年之前的巴黎，人们会发现一个完全不同的city. 选项里面只有D的you可以用作visiting的主语。
当伴随状语的结构用到过去分词的时候也同理：
Based on the four years Behar spent interviewing Esperanza Hernández, a street peddler in the Mexican town of Mexquitic, Hernández felt torn between her Mexican and Indian identities.
A) NO CHANGE
B) the book recounts the tensions Hernandez felt
C) Behar found it fascinating that Hernandez felt torn
D) she recounts the tensions Hernandez felt
这个句子中Based on the four years B spent interviewing EH，指某事物是基于四年来B对EH的采访，based的逻辑主语应当是某个事物或者观点而不是人本身，所以选项里面的the book可以作为based的主语，其他选项都会构成悬垂结构的语病。
伴随状语是介词短语的情况下，同样要注意主语一致性的问题：
Even with its shortcomings, the continued preservation of invaluable locales was made possible by the Antiquities Act of 1906.
A. )NO CHANGE
B. ) the Antiquities Act of 1906 made the continued preservation of invaluable locales possible.
C.) invaluable locales were saved from destruction and their continued preservation was made possible.
D.) the destruction of invaluable locales was prevented with the Antiquities Act of 1906, and it ensured continued preservation of such sites.
这个题目中with its shortcomings是with的介词短语做伴随，its这个物主代词指代的是句中的Act，强调the Antiquities Act of 1906是存在不足的，preservation是并不完美的Act带来的正向结果，因此用preservation做主语的选项都会构成悬垂结构的语病。