句子改错题型，本质上还是考察语义的准确表达。当然，正确语义 的传递，离不开合理的句子结构和基本书面英语的语法。很多童鞋在经过一段时间长难句训练后，可以快速排除诸如缺少谓语动词，主谓不一致等等这些基本错误，但遇到难题，可能两到三个选项都没有这种“一眼就看得出来的”错误，在比较选项之间的语义差别时，就不知道该怎么下手。在这里就帮大家总结一下，哪些因素影响到了语义，看清他们，帮助我们迅速碾碎难题。
1.修饰语位置的改变
修饰语对主句其他单元提供附加或者描述性的信息，其位置的改变导致修饰对象的变化，进而导致语义的改变。SC经常出现这种修饰语位置改变的选项比较，我们需要根据A选项读出作者希望表达的语义，也就是intended meaning，选择语义合乎逻辑的选项。
1.1 Under the new maritime code, even tiny islets can be the basis for claims to the fishery and oil fields of of large sea area.
1.2 Even tiny islets can be the basis for claims to the fishery and oil fields of large sea area under the new maritime code.
上面这两个例句的区别就是under这个介词短语的位置。介词短语既可以修饰名词也可以修饰句子。第一句话里面处在句首，并且用逗号隔开，很清楚的修饰到后面的整个句子，“在新出台的法律条文下，小岛成为一个依据”；第二句介词短语处在句尾，这个时候修饰上就很暧昧，可能修饰前面的sea area，“法律条文下的海域”，也可能修饰整句话，所以肯定第一句语义更加明确，合理。
我们来看一道OG上的例题：
例：His studies of ice-polished rocks in his Alpine homeland, far outside the range of present-day glaciers, led Louis Agassiz in 1837 to propose the concept of an age in which great ice sheets had existed in now currently temperate areas.
(A) in which great ice sheets had existed in now currently temperate areas
(B) in which great ice sheets existed in what are now temperate areas
(C) when great ice sheets existed where there were areas now temperate
(D) when great ice sheets had existed in current temperate areas
(E) when great ice sheets existed in areas now that are temperate
这道题目答案是B，其中副词now是在修饰谓语部分are temperate，目前是温暖的地方；但是E选项，now的位置放到了that从句的前面，这样它就修饰不到that从句里面的are temperate了，直接导致语意错误。
2.修饰语的选择
英语当中有许多不同的修饰语，有同位语，有形容词，副词，介词，独立主格，从句等等。每种修饰语有不同的作用和不同的修饰对象，所以不同形式的修饰语的选择，会造成完全不同的语义
2.1 Tom’s grandmother is his supposed Irish ancestor.
2.2 Tom’s grandmother is his supposedly Irish ancestor.
这两句话语法上都是没有问题的，唯一差别就是suppose这个单词的词性，第一句话用的是形容词，所以它只能修饰后面的名词ancestor，第二句话用的是副词，所以它修饰的是后面的形容词Irish。第一句话语义显然不合理，祖母肯定是ancestor，但祖母有可能不是Irish。
例：The use of lie detectors is based on the assumption that lying produces emotional reactions in an individual that, in turn, create unconscious physiological responses.
(A) that, in turn, create unconscious physiological responses
(B) that creates unconscious physiological responses in turn
(C) creating, in turn, unconscious physiological responses
(D) to create, in turn, physiological responses that are unconscious
(E) who creates unconscious physiological responses in turn
做句子改错题目，有一个原则：如果A选项的语义合理，没有逻辑问题的话，就不要改变句子意思了；除非A选项的语义是错误的，我们才找一个更加符合逻辑的选项。
这里A选项里面划线部分的that从句，其实是一个跳跃修饰，修饰的是前面的emotional reactions。原句的逻辑是撒谎产生心理反应，心理反应导致生理反应。逻辑非常清楚，想想咱们考GMAT，不也是这样吗？在考场上一紧张，就开始手发抖，握不住鼠标了。
对比看E选项，把that改成了who，只能修饰人，这样语义就完全改变了，由心理导致的变成人自己主动发出的了，和原句的intended meaning完全不一样了；而且人自己主动发出来反应，逻辑上也不是很很好：第一，这里是“无意识的”反应；其次，人自己是没法主动控制生理反应的，你不可能在读着这段文字解析的时候就脸红心跳，一定是先有心理变化，才有生理的反应。当然这里的in turn的位置也不如A好，A选项才能更好地修饰create。
3.连接词的改变
连接词除了可以起到连接的作用之外，还可以表达不同的逻辑意思，比如while引导从句的时候可以表达强对比，转折让步等逻辑意思，as引导从句可以表时间，原因等
3.1 Tom eats healthy food, and does exercise regularly.
3.2 Tom eats healthy food, or does exercise regularly.
3.3 Tom does exercise regularly so that he eats healthy food.
这三个例子分别使用了and, or 和so that三种连接方式，第一句话说的是Tom吃健康食品，同时还定期锻炼；第二句话说的是Tom要么锻炼，要么吃健康食物，这两句话都很合理。可是第三句，so that表示因果或者目的，这里两种语义都说不通了。
例：The steel industry has changed radically over the last two decades, as large, integrated companies such as Bethlehem Steel once conducted operations from mining at one end of the process to shipping at the other have greatly downsized, or in some cases shut down altogether.
A. as large, integrated companies such as Bethlehem Steel
B. as large, integrated companies, such as Bethlehem Steel, that
C. with large, integrated companies, such as Bethlehem Steel, that
D. while large, integrated companies, such as Bethlehem Steel, that
E. and large, integrated companies such as Bethlehem Steel
这题原句A选项，as引导原因状语从句，表达的语义是钢铁业发生翻天覆地变化，原因是最大最牛的钢铁企业也裁员或者倒闭了。D选项用了while来连接，然后它只能表达转折，对比之类的，表示不了原因，所以逻辑意思上出了问题。
4.时态的改变
英语的时态和语义是直接挂钩的，在特定的语境下，选择合理的时态才可以表达合理的语义。
4.1 The Millers lived in a hut for three days.
4.2 The Millers have lived in a hut for three days.
这两句话一个是过去时，一个是现在完成时，传达出两种完全不一样的语义；第一句说的是Millers一家过去在小屋子里住了三天，只知道在过去，至于是去年，十年前并不清楚；第二句话说的是Millers一家刚刚住了三天，可以推算出他们一家什么时候住进去的。在一个具体的题目中，具体的语境下，需要选择合理的时态，使得上下文符合逻辑。
例：Nobody knows exactly how many languages there are in the world, partly because of the difficulty of distinguishing between a language and the sublanguages dialects within it, but those who have tried to count typically have found about five thousand.
(A) and the sublanguages or dialects within it, but those who have tried to count typically have found
(B) and the sublanguages or dialects within them, with those who have tried counting typically finding
(C) and the sublanguages or dialects within it, but those who have tried counting it typically find
(D) or the sublanguages or dialects within them, but those who tried to count them typically found
(E) or the sublanguages or dialects within them, with those who have tried to count typically finding
这题答案选A，but后半句说的是那些试图去数语言的人发现有五千种语言。其实中文的这种翻译完全掩盖了英语时态背后所隐含的语义；这里have tried 用的是现在完成时，说的是到目前为止试图去数，所以后面用have found表示到目前为止数出来有多少种语言，这样前后的逻辑才可以搭上去；C选项，将have found改成了find，一般现在时，语义上就和have tried矛盾了，所以时态是错误的。
5.“情景词”的改变或删除
英语中有些重要的“情景词”，删除或者改变它们，会改变整个语境，对句意产生影响。
5.1 Beijing has evolved into a big city.
5.2 Beijing is a big city.
这两句话语法都正确，只是在用词上稍稍发生了改变，背后所隐含的语义完全变了。第一句话谓语用evolve，暗示北京过去不是大城市，现在慢慢演变成了一个大城市；第二句话谓语用is，暗示北京现在是一个大城市，过去是什么样，并不清楚。
5.3 Tom may go to the swimming pool tomorrow.
5.4 Tom will go to the swimming pool tomorrow.
5.5 Tom can go to the swimming pool tomorrow.
这三句话里面may，will 和can，一字之差，却表达完全不同的语义；may 表示可能性，说明是可能去，也可能不去；will表示一定会去；can表示现在条件具备了，比如手头工作完成了，能够去了。
例：A scrub jay can remember when it cached a particular piece of food in a particular place, researchers have discovered, and tend not to bother to recover a perishable treat if stored long enough to have rotted.
A. tend not to bother to recover a perishable treat if
B. they tend not to bother recovering a perishable treat
C. tending not to bother recovering a perishable treat if
D. tends not to bother recovering a perishable treat
E. tends not bothering to recover a perishable treat if
这题主干大致是a scrub jay can remember…..and tend…两个动词原形remember和tend平行并列，都跟在can后面；对比答案D选项，主干变成了a scrub jay can remember….and tends…..这里是can remember和tends 在平行。这种平行差别的对比，可以看出第一句的语义不合逻辑，翻译成灌丛鸦能够记忆，同时能够倾向于。读起来很拗口，因为倾向不是一种能力，不应该用can tend，而是用tends。
小结
句子改错题型的一个基本解题步骤：跳修饰，读主干，理清intended meaning；先排结构错误；再比较选项间的语义差别，挑选最优选项。
读懂语义是做好句子改错的关键，也是很多同学需要努力提高的方面。学习句子改错高效方法不是简单机械的记忆所谓的语法点
，在了解常考的基本句子结构，知道基础的语法知识后，更多的精力应该放在阅读理解上，把常错的考点的题目收集归纳，多多对比，体会出题人的思路和套路，只有这样，你的思路才可能和出题老头的思路有交集。
指出考试经常出现的这些左右语义的因素，相信我们同学做难题的时候会有更好的方向感，思路也会清晰很多。
