我们都知道主语和谓语要保持人称和数的一致，但是这并不能解决同学们在做GMAT句子改错中所遇到的问题。
很多同学仍然不能够辨别出主语所对应的谓语，亦或是谓语所对应的主语，有时遇到好判断的题目，就捡到了便宜，而句子一晦涩难懂就再难分辨，这就导致本是GMAT九大原则中比较简单的主谓一致原则成为了让人既爱又恨的考点。
那么如何攻克SC中的主谓一致原则呢
以下3个例题教会你!
第一种：插入语拦主谓中间
例：
Efforts to equalize the funds available to school districts, a major goal of education reformers and many states in the 1970's, has not significantly reduced the gags existing between the richest and poorest districts.
A. has not significantly reduced the gaps existing
B. has not been significant in reducing the gap that exists
C. has not made a significant reduction in the gap that exists
D. have not significantly reduced the gap that exists
E. have not been significant in a reduction of the gaps existing
同学们很容易就能看出选项中的差别：AB has，CDE have，这个时候只需要判断出主语是谁就可以了，很多同学会选择has是认为主语是goal，实际上要注意这里a major goal of education reformers and many states in the 1970's 是同位语成分，也就是说是一个插入语，找主语时可以自动忽略掉，实际的主语应该是efforts，那么自然ABC就排除了，DE两个选项，很明显D更为简洁，因此选择D。
第二种：定语(从句)在主语后
例：
While larger banks can afford to maintain their own data-processing operations, many smaller regional and community banks are finding that the cost associated with upgrading data-processing equipment and with the development and maintenance of new products and technical staff are prohibitive.
A. cost associated with
B. costs associated with
C. costs arising from
D. cost of
E. costs of
这道题目的选项最明显的差别也是一个2/3分，需要同学们先判断出cost这个主语到底应该用单数还是复数，那么我们往后找它的谓语动词，谓语是谁?谓语是are。为什么?因为associated with upgrading data-processing equipment and with the development and maintenance of new products and technical staff整个这么长全部都是cost的后置定语，只不过这个后置定语有了个并列，导致它超长，但这仍然是过去分词短语做后置定语的情况，因此应迅速判断出cost后都是定语成分，使劲往后找谓语are，从而判断出cost应该为复数。同样地，如果cost后不再是一个长长的分词短语做后置定语，而是一个定语从句，我们也应该迅速把它略过。BC中再根据平行原则选择B。
第三种：of 所有格搞迷惑
例：
The lack of complete historical records from the mid-to-late 1800's have made some Black inventions difficult to trace to their originators.
A. have made some Black inventions difficult to trace to their originators.
B. have made for difficulties in tracing some inventions by Blacks to their originators
C. have made it difficult to trace some inventions by Blacks to their originators
D. has made it difficult to trace some inventions to their Black originators
E. has made it difficult in tracing some Black inventions to their originators
首先，have和has中做选择应判断主语是哪一个，of所有格的表达，of后是修饰语，of前为被修饰词，翻译成汉语应颠倒过来，核心词应该是被修饰词，也就是of前的名词。因此这道题中，主语为lack，动词也就自然应该用has了，最后再根据习惯用语，选择出答案D。
然而值得同学们注意的是，还有一种情况即使出现了of所有格，紧随其后的谓语动词也不一定会与of前保持一致，那就是在of所有格后有定语从句，从句中出现的动词需要根据定语从句的修饰关系判断。
例：
The list of animals that exhibits a preference of either using the right or the left hand (i.e., claw, paw, or foot) has been expanded to include the lower vertebrates.
A. exhibits a preference of either using the right or the left hand (i.e., claw, paw, or foot) has been expanded to include
B. exhibits the preference to use either the right or the left hand (i.e., claw, paw, or foot) has been expanded and includes
C. exhibit a preference in either using the right or the left hand (i.e., claw, paw, or foot) has been expanded to include
D. exhibit a preference for using either the right or the left hand (i.e., claw, paw, or foot) has been expanded to include
E. exhibit the preference as to either using the right or the left hand (i.e., claw, paw, or foot) has been expanded and includes
Of所有格后有一个that引导的定语从句，而这个定语从句修饰的是它的主语animals，因此后面的动词exhibit就不能再加s了。
