GMAT逻辑推断题两招搞定

推断题在GMAT逻辑中算是入门题型，它要求你承认文本中给出的信息均为真，此时能够推出哪一个选项，提问形式有 “which of the following inferences is best supported by the passage” 或 “if the statements above are true, then which one of the following must also be true” 等。但对于刚接触GMAT逻辑的同学而言，还是会因长句难懂、时间不够等原因选错答案。举例如下：

People tend to estimate the likelihood of an event's occurrence according to its salience; that is, according to how strongly and how often it comes to their attention. By placement and headlines, newspapers emphasize stories about local crime over stories about crime elsewhere and about many other major events.

It can be concluded on the basis of the statements above, if they are true, which of the following is most probably also true?

(A) The language used in newspaper headlines about local crime is inflammatory and fails to respect the rights of suspects.
　　(B) The coverage of international events in newspapers is neglected in favor of the coverage of local events.
　　(C) Readers of local news in newspapers tend to overestimate the amount of crime in their own localities relative to the amount of crime in other places.
　　(D) None of the events concerning other people that are reported in newspapers is so salient in people's minds as their own personal experiences.
　　(E) The press is the news medium that focuses people's attention most strongly on local crimes.

文本信息用了两句话，共50词；提问和选项有130词。这么长的题目，考试要求是两分钟内选出答案。对考生而言这是何等的残酷。现在就来教大家两招，在短时间内尽量提高正确率，甚至直接做出答案。

1. 无关词排除法

推断题是一个对讨论范围要求非常严格的题型。由于正确选项由给出的信息推知，因此选项中讨论的内容必须来自给出的信息，不能随性往外延伸。比如原文只说苹果营养丰富，你就不能说香蕉营养丰富或苹果口感很棒。如：

Experienced pilots often have more trouble than novice pilots in learning to fly the newly developed ultralight airplanes. Being accustomed to heavier aircraft, experienced pilots, when flying ultralight craft, seem not to respect the wind as much as they should.

The passage implies that the heavier aircraft mentioned above are

(A) harder to land than ultralight aircraft
　　(B) not as popular with pilots as ultralight aircraft
　　(C) not as safe as ultralight aircraft
　　(D) more fuel-efficient than ultralight aircraft
　　(E) easier to handle in wind than ultralight aircraft

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如果我们看选项时有意识地用上无关词排除法，我们很快发现ABCD四个选项中的land（着陆）、popular（受欢迎与否）、safe（安全性）、fuel-efficient（燃油经济性）均未在原文中有任何相关的提及，故全部排除，只能选E。

2. 公共元素连接法

原文给出的几句信息中（特别是两句），如果有公共元素，我们可以把公共元素拿掉，再把剩下的东西拼在一起，让剩下的东西产生联系，很有可能就是正确答案。如“所有老师都放假。我是老师。”拿掉公共元素“老师”，结论就是“我放假”。

Increase in the level of high-density lipoprotein (HDL) in the human bloodstream lower bloodstream-cholesterol levels by increasing the body’s capacity to rid itself of excess cholesterol. Levels of HDL in the bloodstream of some individuals are significantly increased by a program of regular exercise and weight reduction.

Which of the following can be correctly inferred from the statements above?

(A) Individuals who are underweight do not run any risk of developing high levels of cholesterol in the bloodstream.
　　(B) Individuals who do not exercise regularly have a high risk of developing high levels of cholesterol in the bloodstream late in life.
　　(C) Exercise and weight reduction are the most effective methods of lowering bloodstream cholesterol levels in humans.
　　(D) A program of regular exercise and weight reduction lowers cholesterol levels in the bloodstream of some individuals.
　　(E) Only regular exercise is necessary to decrease cholesterol levels in the bloodstream of individuals of average weight.

这一题原文有两句话，第一句讲到HDL和bloodstream cholesterol的关系，第二句讲到HDL和exercise and weight reduction的关系。两句话的公共元素就是HDL，因此正确选项应该要让去掉公共元素后剩下的bloodstream cholesterol和exercise and weight reduction产生联系。据此来看，正确选项应该是D。

需要注意的是，这两个方法本身并非相互排斥、非此即彼，我们在做题时可以把这两个方法结合起来，读完原文和提问知道是推断题后，可以自己根据公共元素连接法构想出一个大致的正确答案，再把无关词排除法运用在筛选选项的过程中。

现在我们在回过头来看第一个例子。原文还是两句话，第一句话讲的是“人们认为的一件事情发生的可能性的高低”与“这件事情的salience——被提及的强度与频率”的关系，第二句话讲的是“报纸总是报道本地犯罪的新闻”。

咋一看，似乎并没有公共元素，其实第一句的“高salience”就是第二句的“总是报道”，或者说原文的词组emphasize A over B，因此取出公共元素后的正确选项应该把“人们认为的一件事情发生的可能性的高低”与“本地犯罪”结合，即人们认为本地犯罪发生的可能性很高。

然后我们再去筛选选项：A项的language明显是无关词；B项的international events有点像无关词，但原文讲到过elsewhere，先保留；C项符合我们的预估；D项personal experiences为无关词；E项的most strongly语气过分绝对，回文一看未有此意。比较B和C，B的neglect含义也过头了，C最正确。

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