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老程说 | 托福阅读之反向推理

2019-11-11 20:20:15
在托福阅读里大多数出现的是“正向推理”,也就是正确选项和原文的概念是一致的范畴。然而,也有一部分是“反向推理”,即正确选项和原文的概念是相反的范畴。
 
举个栗子:原文说“遇见你之前我是沉迷游戏无法自拔的。”如果利用反向推理出题,正确选项可能是“遇见你之后我就不在沉迷游戏无法自拔了。”像这种带有时间或事件的句子很容易出现反向推理题。它涉及的题型不一定只是推断题,还有可能出现在细节题里。
 
我们来看个题目:
After the peak year of 1957, the birth rate in Canada began to decline. It continued falling until in 1966 it stood at the lowest level in 25 years. Partly this decline reflected the low level of births during the depression and the war, but it was also caused by changes in Canadian society. Young people were staying at school longer, more women were working, young married couples were buying automobiles or houses before starting families, rising living standards were cutting down the size of families. It appeared that Canada was once more falling in step with the trend toward smaller families that had occurred all through the Western world since the time of the Industrial Revolution.
 
It can be inferred from the passage that before the Industrial Revolution
A. families were larger
B. population statistic were unreliable
C. the population grew steadily
D. economic conditions were bad
 
正确答案:A
这一题就是典型反向推理逻辑了。原文说“Canada families 从the Industrial Revolution以后就变得smaller”,相反就是“Canada families 在the Industrial Revolution以前是larger”。
 
今天我们把反向推理分成两大类来展示
(1) 时间点/事件点前后变化之反向推理
(2) 反义词反向推理
 
01
时间点/事件点前后变化之反向推理
 
例1 TPO4
Oil pools are valuable underground accumulations of oil, and oil fields are regions underlain by one or more oil pools. When an oil pool or field has been discovered, wells are drilled into the ground. Permanent towers, called derricks, used to be built to handle the long sections of drilling pipe. Now portable drilling machines are set up and are then dismantled and removed. When the well reaches a pool, oil usually rises up the well because of its density difference with water beneath it or because of the pressure of expanding gas trapped above it. Although this rise of oil is almost always carefully controlled today, spouts of oil, or gushers, were common in the past. Gas pressure gradually dies out, and oil is pumped from the well. Water or steam may be pumped down adjacent wells to help push the oil out. At a refinery, the crude oil from underground is separated into natural gas, gasoline, kerosene, and various oils. Petrochemicals such as dyes, fertilizer, and plastic are also manufactured from the petroleum.
 
Which of the following can be inferred about gushers?  
A. They make bringing the oil to the surface easier.
B. They signal the presence of huge oil reserves.
C. They waste more oil than they collect.
D. They are unlikely to occur nowadays.
 
正确选项:D
原文说“..... 在过去,gushers是普遍的”。那就反向推测出“现在gushers不普遍了”。咱们类比下,“在过去麒麟是常见的”。那就反向推测出“现在麒麟不常见了”。也就是不怎么出现了。
 
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.
 
Which of the following can be inferred about canal building?
A. Canals were built primarily in the south of England rather than in other regions.
B. Canal building decreased after the steam locomotive was invented.
C. Canal building made it difficult to study rock strata which often became damaged in the process.
D. Canal builders hired surveyors like Smith to examine exposed rock strata.
 
正确选项:B
原文说“在蒸汽机出现之前,运河建设达到顶峰。那就反向推测出“在蒸汽机出现之后,运河建设就不是顶峰,=走下坡路了。”我们做个类比,“期中考试前,我成绩一直是班级第一。” 那就反向推测出“期中考试之后,我成绩就不是班级第一,=走下坡路了。”
 
02
反义词反向推理
 
We all know that many more people today are right-handed than left-handed. Can one trace this same pattern far back in prehistory? Much of the evidence about right-hand versus left-hand dominance comes from stencils and prints found in rock shelters in Australia and elsewhere, and in many Ice Age caves in France, Spain, and Tasmania. When a left hand has been stenciled, this implies that the artist was right-handed, and vice versa. Even though the paint was often sprayed on by mouth, one can assume that the dominant hand assisted in the operation.
 
2. It can be inferred from paragraph 1 that even when paint was sprayed by mouth to make a hand stencil 
A. there was no way to tell which hand was stenciled
B. the stenciled hand was the weaker hand
C. the stenciled hand was the dominant hand
D. artists stenciled more images of the dominant hand than they did of the weak
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