备考托福是一场漫长的攻坚战，需要同学们不断地储备丰富的托福知识，托福阅读一直是同学们心中的老大难，接下来就跟着北雅一起学习托福阅读推断题之解题思路。

OG上将推断题定义为检查考生对文章中强烈建议但绝不明说观点(strongly implied but not explicitly stated in the text)的理解程度，属于理解性题目，题目要求如下：

　　Which of the following can be inferred from paragraph 2 about X?

　　According to paragraph 5, what does the author imply about X ?

　　Paragraph 1 suggests which of the following about X?

　　According to paragraph 3, what do Y indicate about X?

　　题干中有出现infer, imply, indicate或suggest这四个单词，我们就判定一个题目为推断题，那推断题如何解答呢?

　　第一步，判断题型。我们拿到题目，看到上面四个单词中的任何一个，心中就想着这是推断题，推断题的做题忠旨是文章中强烈建议但未明说的。

　　第二步，审清题干。明白题目是要我们根据哪段进行推测，推测关于什么的。

　　第三步，原文定位。根据题干中我们找到的信息点，回到原文定位，找到相关句。

　　第四步，推测+判断。根据相关句进行正向或逆向的推理，最后择优而选，确定答案。

　　前三步，可以借用做事实信息题的方法来做，最后一步的推测，相对于正向推理，逆向推理对同学们简单一些，回到原文中定位，发现相关句中存在着对比或转折的，直接否定前者，得出答案，例如TPO2中的The Origins of Cetaceans 的第2题，让你推测关于early sea otters的，回到原文中定位，你会发现，关键句中存在着一个unlike，说不像sea otters，想象一下早期鲸类比较困难(not easy=difficult)，那我们逆推一下，不就是说想象早期sea otters长什么样比较容易，正确答案中出现了not difficult，所以这道题很简单，当然ETS不会一直都出这么简单的推断题，只是给大家一个答题的方向，另外，ETS经常会在有时间对比处出推断题，这时候我们逆向推理就可以得出正确答案，下面看一个例题：

　　3. Which of the following can be inferred from paragraph 2 about canal building?

　　○ Canals were built primarily in the south of England rather than in other regions.

　　○ Canal building decreased after the steam locomotive was invented.

　　○ Canal building made it difficult to study rock strata which often became damaged in the process.

　　○ Canal builders hired surveyors like Smith to examine exposed rock strata.

　　Paragraph 2: This was before the steam locomotive, and canal building was at its height. The companies building the canals to transport coal needed surveyors to help them find the coal deposits worth mining as well as to determine the best courses for the canals. This job gave Smith an opportunity to study the fresh rock outcrops created by the newly dug canal. He later worked on similar jobs across the length and breadth of England, all the while studying the newly revealed strata and collecting all the fossils he could find. Smith used mail coaches to travel as much as 10,000 miles per year. In 1815 he published the first modern geological map, "A Map of the Strata of England and Wales with a Part of Scotland," a map so meticulously researched that it can still be used today.

　　解析：第一步，我们看到infer判断为推断题。第二步，审题得到的信息点是第2段和canal building。第三步，回到原文定位，相关句为第一句，This was before the steam locomotive, and canal building was at its height.出现了before steam locomotive，有时间对比，canal building was at its height , at one's height处于顶峰。那第四步我们就可以逆向推理到after steam locomotive，canal building 下滑，判定四个选项中只有B符合我们的推测，所以正确选项为B，而ACD都是迷惑你的无关选项。

　　逆推比较好理解，而正推同学们觉得难的原因是不好把握度，很容易加上自己的主观判断就推过了，这时候我们可以把它当做事实信息题去做，因为你要基于原文进行推测，那么讨论的角度和情感色彩要与原文的保持一致，所以做题的另外一条原则是don't contradict with the main idea of the passage，推测的时候我们可以用演绎或者归纳的方法得出正确答案，也可以借用文章主旨和情感态度选出正确答案，看如下例题：

　　10. According to paragraph 4, what do the 2003 Global Surveyor data suggest about Mars?

　　○Ancient oceans on Mars contained only small amounts of carbon.

　　○The climate of Mars may not have been suitable for the formation of large bodies of water.

　　○Liquid water may have existed on some parts of Mars' surface for long periods of time.

　　○The ancient oceans that formed on Mars dried up during periods of cold, dry weather.

　　Paragraph 4: These ideas remain controversial. Proponents point to features such as the terraced "beaches" shown in one image, which could conceivably have been left behind as a lake or ocean evaporated and the shoreline receded. But detractors maintain that the terraces could also have been created by geological activity, perhaps related to the geologic forces that depressed the Northern Hemisphere far below the level of the south, in which case they have nothing whatever to do with Martian water. Furthermore, Mars Global Surveyor data released in 2003 seem to indicate that the Martian surface contains too few carbonate rock layers-layers containing compounds of carbon and oxygen-that should have been formed in abundance in an ancient ocean. Their absence supports the picture of a cold, dry Mars that never experienced the extended mild period required to form lakes and oceans. However, more recent data imply that at least some parts of the planet did in fact experience long periods in the past during which liquid water existed on the surface.

　　解析：根据关键词我们定位到文段的中间部分：Mars Global Surveyor data released in 2003 seem to indicate that the Martian surface contains too few carbonate rock layers-layers containing compounds of carbon and oxygen-that should have been formed in abundance in an ancient ocean.这道题可以当做事实信息题去做，但注意不是原文的简单重复，suggest 是原文中indicate的同义转换，我们只要找到what就好了，原文that后面是重点，出现了too few, should have, 情感态度推测一下，持否定态度，也就说说形成 an ancient ocean不太可能，我们看选项，A中说Ancient oceans on Mars contained only small amounts of carbon.主客体与原文矛盾，排除;B选项 The climate of Mars may not have been suitable for the formation of large bodies of water.说不适合形成大量的水，持否定态度，符合原文，保留;C选项Liquid water may have existed on some parts of Mars' surface for long periods of time.相关句中未提及，排除;D选项The ancient oceans that formed on Mars dried up during periods of cold, dry weather. 说的是ancient oceans没有，而不是原来有后来干涸了，与原文不符，排除，所以正确答案为B。