不同的同學有不同的擅長點，就像面對托福閱讀一樣，如果要說托福閱讀的十種題型，哪種最難，千人千答案，但如果我們從數據的角度來統計，就會發現，大多數的同學，對托福閱讀的小結題和推斷題，往往是要么因為時間，要么斟酌著不知道該選哪一項，從而大多數考生對這兩種題型比較抗拒，下面我們就為大家分享一下如何用正逆向思維解決托福閱讀推斷題。
說到推斷題，不要抗拒，更不要苦惱，雖然表面是推斷題看著是云里霧里，但其實托福閱讀沒有你想象的那么難，因為托福作為標準化的考試，肯定會有一定的答題技巧，托福文章有很清晰的邏輯結構，每個自然段往往是按照TS (Topic Sentence) + SD (Supporting details)展開的，而文章多半是按Introduction + Aspects + Attitudes展開的。只有明白了文章的寫作思路才能更好更快的做對題目，作者必定是按照一定的行文順序編排段落的，如果畫一個水平軸作為事件發展的順序，推斷題是讓你從這個軸上的某一個點去推測，無非就兩個方向，順著軸發展的方向或者逆著軸發展的方向，也就是我們接下來要說的用正向和逆向思維去解決推斷題。
OG上將推斷題定義為檢查考生對文章中強烈建議但絕不明說觀點(stronglyimplied but not explicitly stated in the text)的理解程度，屬于理解性題目，題目要求如下：
Paragraph 2 suggests which of the following about X?
Which of the following can be inferred from paragraph 2 about X?
According to paragraph 3, what do Y indicate about X?
According to paragraph 4, what does the author imply about X?
題干中有出現infer, imply, indicate或suggest這四個單詞，我們就判定這個題目為推斷題，那么推斷題應該如何解答呢?
第一步，判斷題型。我們拿到題目，看到上面四個單詞中的任何一個，心中就想著這是推斷題，推斷題的做題宗旨是文章強烈暗示，要通過文章內容進行合理推斷。
第二步，審清題干，原文定位。仔細閱讀題干，弄清題干內容，推斷方向，帶著題干核心信息到文章中準確定位。
第三步，推測+判斷。根據相關句進行正向或逆向的推理，最后擇優而選，確定答案。
正向推斷：和事實信息題做題方法一樣，答案就是定位的句子的同義改寫。
逆向推斷：大致分為兩種，一種是時間，第二種是兩類事物的對比。
第一種，題干中往往會出現表示時間的信息，比如：after 1932, since early years ofthe 19th century. 例如TPO 20 Passage 1 Western Migration Q1:
Paragraph 1: The story of the westward movement of population in the US is, in the main, the story of the expansion of American agriculture of the development of new areas for the raising of livestock and the cultivation of wheat, corn, tobacco, and cotton. After 1815, improved transportation enabled more and more western farmers to escape aself-sufficient way of life and enter a national market economy during periods when commodity prices were high, the rate of westward migration increased spectacularly。
What can be inferred from paragraph 1 about western farmers prior to 1815?
○They had limited their crop production to wheat, corn,tobacco and cotton。
○They were able to sell their produce at high prices
○They had not been successful in raising cattle。
○They did not operate in a national market economy。
題干中出現了兩個信息，一個是western farmers, 一個是prior to 1815, 帶著兩條信息去文中定位，定位在第一段第四行，但是文章中沒有提到1815年之前，只有1815年之后，答案其實很簡單，只要把1815年之后的內容看懂了，并且在這個內容前面加not即可。舉個簡單的例子，“從現在起Jessica是個姑娘”，“請問你能推斷出昨天Jessica怎么了么?”可能很多人想到“是不是Jessica做了變性手術?”，其實這就算過分推斷了，答案就是Jessica昨天不是個姑娘。言歸正題，文中說到，改善的交通使得越來越多的西部農民擺脫了自給自足的生活，并且進入了國家性的市場經濟，那個時候貨物的價格很多，所以向西遷移的速率也大幅增長。
第二種：兩類事物的對比，往往文中會出現表示對比的關系詞：by contrast, unlike, while,whereas, on the contrary, in comparison to, distinct from, different from等詞。例如TPO 2中的The Origins of Cetaceans的第2題，讓考生推測關于early sea otters的，回到原文中定位，會發現關鍵句中存在著一個unlike, 說不像sea otters, 想象一下早期鯨類比較困難(not easy=difficult)，那我們逆推一下，不就是說想象早期sea otters長什么樣比較容易，正確答案中出現了not difficult, 所以這道題很簡單。當然ETS不會一直都出這么簡單的推斷題，這里只是給大家一個答題的方向。
Paragraph 4: These ideas remain controversial.Proponents point to features such as the terraced "beaches" shown inone image, which could conceivably have been left behind as a lake or oceanevaporated 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 anancient 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 infact experience long periods in the past during which liquid water existed onthe surface。
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 duringperiods of cold, dry weather。
解析：根據關鍵詞我們定位到文段的中間部分：Mars Global Surveyor data releasedin 2003 seem to indicate that the Martian surface contains too few carbon aterock layers-layers containing compounds of carbon and oxygen-that should have been formed in abundance in an ancient ocean。這道題可以當做事實信息題去做，但注意不是原文的簡單重復，suggest 是原文中indicate的同義轉換，我們只要找到what就好了，原文that后面是重點，出現了too few, should have,
情感態度推測一下，持否定態度，也就說說形成 an ancient ocean不太可能，我們看選項，A中說Ancient oceans on Mars contained onlysmall amounts of carbon。主客體與原文矛盾，排除;B選項 The climate of Mars may not have been suitable for the formation oflarge bodies of water。說不適合形成大量的水，持否定態度，符合原文，保留;C選項Liquid water may have existed on some parts of Mars' surface forlong periods of time。相關句中未提及，排除;D選項The ancient oceans that formed on Mars dried up during periods ofcold, dry weather. 說的是ancient oceans沒有，而不是原來有后來干涸了，與原文不符，排除，所以正確答案為B。
面對托福閱讀推斷題，不論是正推還是逆推，關鍵是大家要保持冷靜的頭腦，從事件發展的時間軸或者事件水平軸上進行原因的推斷，找某個突破點，依據原文的內容，找出相應的根據，那么你的托福閱讀推斷題的正確率，一定會很好的提升，不信，你現在就可以實踐一下。