推断题Inference Question，又叫推理题，这种题型是托福阅读中较难的题型之一，也是考生们最容易丢分的一种题型。原因是：相比于其他大部分题型，比如说事实信息题"看到即答案"的简单逻辑，推理题的"模糊"逻辑会让我们无从下手。

它通常会问我们："What can we infer about XXX"，也就是关于XXX我们可以推理出什么？看到这里从小到大做习惯了中国式推理题的学生们就会激动了，立马把自己想象成名侦探柯南，准备好好的抽丝剥茧推理一下。但是，请注意：在托福阅读考试中，做推理题一定要学会"控制智商"！其实很多做过TPO的同学会发现推理题的答案有的时候简单直白到让人脸红耳赤的程度，而那个让你觉得很正确的选项一般来说都存在"过度联想"，或者说"推理过度"的情况。而有些题目做的比较多的同学，做题时会提醒自己不要推理过度，这个时候又会出现另一种情况，叫做"推理不足"。这两种情况也是同学们在做推理题中经常出现的，难以拿捏推理的这个"度"，导致推理题的正确率就不高。那么，在这里我们就一起来看看推理题的本质，找到正确的解题方法。

首先，我们可以把它的题目分为两类。 一类是（1）题干定位型，一类是（2）选项定位型。怎么样区分呢？题干定位题，顾名思义，就是我们通过题目中的词可以定位到原文中答案所在的位置从而选出答案；而选项定位型则是指我们没办法通过题目来定位的情况，比如说：题目问What can be inferred about fish?而原文中整段都在讲fish，你就没有办法去具体定位，这个时候我们就可以利用选项去定位原文。

好，区分了题目的两种类型，接下来我们要掌握的就是应对它们的解题方法了。这里用一个思维导图就非常清晰了：

接下来，我们来讲题干定位型中的第一种逻辑推理--反向推理。

我们在做题时要意识到：如果这道题可以通过题干定位到，那么这道题就不是难题。我们需要做的就是紧扣定位区间，在这个定位区间中找到依据并根据这个依据推断出正确选项，需注意的是：虽然我们做的是推理题，但一定也是有依据的，一定要找到你的"证据"所在。

那么，什么是反向推理？就是学术写作中，当我们将事物按照某种标准进行分类后，分类的内容既不重合也不丢失。比如我们把A分成X和Y,X和Y之间没有重合的部分，同时X和Y合并构成A,也不会丢失A的某一部分。这样一来，当我们知道X所具有某一个特性，就能推出Y不具有这样的特性，这就是反向推理。我们拿一道TPO的题目实践一下。

It should be obvious that cetaceans - whales, porpoises, and dolphins - are mammals. They breathe through lungs, not through gills, and give birth to live young. Their streamlined bodies, the absence of hind legs, and the presence of a fluke and blowhole cannot disguise their affinities with land-dwelling mammals. However, unlike the cases of sea otters and pinnipeds (seals, sea lions, and walruses, whose limbs are functional both on land and at sea), it is not easy to envision what the first whales looked like. Extinct but already fully marine cetaceans are known from the fossil record. How was the gap between a walking mammal and a swimming whale bridged? Missing until recently were fossils clearly intermediate, or transitional, between land mammals and cetaceans.

Which of the following can be inferred from paragraph 1 about early sea otters?

A.It is not difficult to imagine what they looked like.

B.There were great numbers of them.

C.They lived in the sea only.

D.They did not leave many fossil remains.

这道题是非常经典的题干定位、反向推理。题干中的sea otter, 定位到的区间为unlike the cases of sea otters and pinnipeds (seals, sea lions, and walruses, whose limbs are functional both on land and at sea), it is not easy to envision what the first whales looked like.根据unlike推出sea otter情况与cetacean相反，因此选A。

我们再来看一道题目：

A symbiotic relationship is an interaction between two or more species in which one species lives in or on another species. There are three main types of symbiotic relationships: parasitism, commensalism, and mutualism. The first and the third can be key factors in the structure of a biological community; that is, all the populations of organisms living together and potentially interacting in a particular area.

Which of the following statements about commensalism can be inferred from paragraph 1?

A.It excludes interactions between more than two species.

B.It makes it less likely for species within a community, to survive.

C.Its significance to the organization of biological communities is small.

D.Its role in the structure of biological populations is a disruptive one.

根据题干的commensalism, 可以找到定位区间"There are three main types of symbiotic relationships: parasitism, commensalism, and mutualism. The first and the third can be key factors in the structure of a biological community"。第一句话罗列了三种关系，第二句话强调了第一种和第三种是key factor，那么没有提到的第二种--也就是题干所问的这一种，反推可知commensalism不是key factor。所以答案就是C, its significance is small.C选项只是对于我们推出的"commensalism不是key factor"进行了同意改写，同学们要能够看出来。

最后，我们来看一道难题：

The Whigs, in contrast, viewed government power positively. They believed that it should be used to protect individual rights and public liberty, and that it had a special role where individual effort was ineffective. By regulating the economy and competition, the government could ensure equal opportunity. Indeed, for Whigs the concept of government promoting the general welfare went beyond the economy. In particular, Whigs in the northern sections of the United States also believed that government power should be used to foster the moral welfare of the country. They were much more likely to favor social-reform legislation and aid to education.

1.Which of the following can be inferred from paragraph 5 about variations in political beliefs within the Whig Party?

A.They were focused on issues of public liberty.

B.They caused some members to leave the Whig party.

C.They were unimportant to most Whigs.

D.They reflected regional interests.

根据题干的Whigs Party回原文中定位，我们可以定位到三处，这时候同学们要注意了，原文问的是我们可以推出以下哪个结论，关于Whigs Party内部政治信仰的不同，重点在"不同"上。那么定位的第一处"The Whigs viewd…"说的是整个党派的看法，因为没有体现不同所以可不看；第二处"for Whigs the concept of…"同样也是整个党派的集体看法，可以不看；第三处"Whigs in the northern section of the United State"说的是美国南部的辉格党的看法，那么我们就可以推出其他地方的辉格党就会存在其他的观点。所以他们的不同体现在地区的想法不同上，答案选D。

这里通过难度不同的三个例子分析了推理题中题干定位型的反向推理是怎么运用的，希望大家能有所收获！