托福阅读技巧之正向和逆向思维

cultivation of wheat, corn, tobacco, and cotton. After 1815, improved transportation enabled more and more western farmers to escape a self-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.

　　题干中出现了两个信息，一个是western farmers, 一个是prior to 1815, 带着两条信息去文中定位，定位在第一段第四行，但是文章中没有提到1815年之前，只有1815年之后，答案其实很简单，只要把1815年之后的内容看懂了，并且在这个内容前面加not即可。举个简单的例子，“从现在起Jessica是个姑娘”，“请问你能推断出昨天Jessica怎么了么?”可能很多人想到“是不是Jessica做了变性手术?”，其实这就算过分推断了，答案就是Jessica昨天不是个姑娘。言归正题，文中说到，改善的交通使得越来越多的西部农民摆脱了自给自足的生活，并且进入了国家性的市场经济，那个时候货物的价格很多，所以向西迁移的速率也大幅增长。

　　第二种：两类事物的对比，往往文中会出现表示对比的关系词：by contrast, unlike, while, whereas, on the contrary, in comparison to, distinct from, different from等词。例如TPO 2中的The Origins of Cetaceans的第2题，让考生推测关于early sea otters的，回到原文中定位，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，这里只是给大家一个答题的方向。

　　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.

　　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.

　　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。

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