托福阅读的成败很大程度上取决于考生对词汇和句子之间逻辑关系的把握。关于托福词汇的学习策略在本书前面已经有详细论述，所以这里只讨论句子之间逻辑关系的把握。由于句子简化题、句子插入题、推理题等几乎所有托福阅读题型都与句子之间逻辑关系有密切联系，在讨论各种题型时都会详细阐述句子之间逻辑关系及其把握策略，因此这里只概要地罗列托福阅读中涉及的主要逻辑关系以及它们与解题的关系。
托福阅读主要涉及五大逻辑关系：因果关系、对比转折关系、比较关系、否定关系与并列递进关系。不同的逻辑关系以不同的词汇表达，这些词汇既包含关联词，像while, but(表示对比转折关系)等，也包含一些实词，如lead to (表示因果关系)。表示上述五大逻辑关系的常见词汇如下：
一)因果关系
1. 显性因果：
因：because, because of, for, as, since, in that, on account of, with(由于，随着)
果：so, so that, therefore, thereby, as a result, hence, thus, consequently, accordingly
2. 隐性因果：
a. 导致(因—果)：cause, reason(推断), lead to, give rise to, result in, render, make, let, ask, support, push, stimulate, spark, spur, fuel, produce, be responsible for
b. 由……而来(果—因)：result from, derive from, originate from, initiate from, stem from, be responsive to, be attributable to
c. 反映/体现(果—因)：reflect, present, demonstrate, suggest, imply, show
d. 考虑到，依赖于(果—因)：given, considering, concerning, in view of, thanks to; rely on, depend on, resort to, according to
e. 条件关系：when, once, as soon as, as long as
f. 被动语态(by之后为原因)
g. 分词短语、不定式、独立主格做状语
二)对比转折关系
1. 对比：while, whereas; on the other hand, conversely, on the contrary, in contrast; unlike, different from; differ; before, prior to, after
2. 转折：but, although, despite, in spite of, nevertheless, notwithstanding, however
三)比较关系
1. 比较级：as … as, more … than, -er than, less … than
2. 最高级
a. 本身有最高级含义：maximum, minimum, peak, outstanding, top
b. 本身程度比较深：amazing, surprising, astonishing, prohibitively high
c. 否定+比较=最高级
3.
a. 变化：change, alter, vary, modify, revise, increase, decrease, enhance, diminish, develop, progress, advance, improve, retreat, degenerate, continue, remain
b. 差异：different, distinct, distinguish, separate, same, similar, comparable, compare … to
c. 超越：surpass, exceed, excel, over
四) 否定关系
1. 显性否定：no, not, never, nor, none, neither
2. 隐性否定：fail to, refuse, remove, miss, reject, absence of, lack of
3. 否定前缀：a-, ab-, dis-, il-, im-, in-, non-, un-
4. 双重否定：not fail to, not illegal=legal, not uncommon=common
五) 并列递进关系
and, furthermore, moreover, in addition, beyond that, as well as
下面以对比转折关系为例说明如何根据逻辑关系破解阅读问题。
例一(词汇题)
Paragraph 3: At times, it is actually possible to watch the effects of natural selection in host-parasite relationships. For example, Australia during the 1940 s was overrun by hundreds of millions of European rabbits. The rabbits destroyed huge expanses of Australia and threatened the sheep and cattle industries. In 1950, myxoma virus, a parasite that affects rabbits, was deliberately introduced into Australia to control the rabbit population. Spread rapidly by mosquitoes, the virus devastated the rabbit population. The virus was less deadly to the offspring of surviving rabbits, however, and it caused less and less harm over the years. Apparently, genotypes (the genetic make-up of an organism) in the rabbit population were selected that were better able to resist the parasite. Meanwhile, the deadliest strains of the virus perished with their hosts as natural selection favored strains that could infect hosts but not kill them. Thus, natural selection stabilized this host-parasite relationship. (TPO 17)
The word devastated in the passage is closest in meaning to
(A)influenced
(B)infected
(C)strengthened
(D)destroyed
被考词汇devastated所在句子的下一个句子中有however表示对比转折关系： The virus was less deadly to the offspring of surviving rabbits, however, and it caused less and less harm over the years，说明devastated与less deadly的意思相反，而less表示否定，那么devastated的意思相当于deadly(致命的)，与此意思接近的为第四个选项 ：“破坏”，因此它是正确选项。
例二(事实信息题)
Paragraph 6: With the advent of projection, the viewer's relationship with the image was no longer private, as it had been with earlier peepshow devices such as the Kinetoscope and the Mutoscope, which was a similar machine that reproduced motion by means of successive images on individual photographic cards instead of on strips of celluloid. It suddenly became public---an experience that the viewer shared with dozens, scores, and even hundreds of others. At the same time, the image that the spectator looked at expanded from the minuscule peepshow dimensions of 1 or 2 inches (in height) to the life-size proportions of 6 or 9 feet.
Which of the following is mentioned in paragraph 6 as one of the ways the Mutoscope differed from the Kinetoscope?
(A)Sound and motion were simultaneously produced in the Mutoscope.
(B)More than one person could view the images at the same time with the Mutoscope.
(C)The Mutoscope was a less sophisticated earlier prototype of the Kinetoscope.
(D)A different type of material was used to produce the images used in the Mutocope.
这是一道事实信息题，根据问题中的关键词Mutoscope和Kinetoscope定位到段落首句，问题中的differed from要求我们在文中寻找对比关系。首句中的which引导的非限定性定语从句补充说明Mutoscope和Kinetoscope的相同点和不同点，其中instead of 提示二者之间的区别，即对比关系：on individual photographic cards instead of on strips of celluloid(在卡片上而不是电影胶片上)。由此可见Mutoscope和Kinetoscope成像的材料不同。选项4符合此意，为正确答案。
例三(推理题：直接对比)
Paragraph 1: 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.
问题中的infer表明这是一道推理题。根据问题中的关键词 sea otters 定位到文中第三句： 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，其中的unlike表明sea otters和first whales不同，构成对比关系，那么可以推出：不难想象sea otters早期的样子。因此选项1为正确答案。其他选项涉及的数量和栖息环境在原文中都未提到。
例四(推理题：时间对比)
…The nineteenth century brought with it a burst of new discoveries and inventions that revolutionized the candle industry and made lighting available to all. In the early-to-mid-nineteenth century, a process was developed to refine tallow (fat from animals) with alkali and sulfuric acid. The result was a product called stearin. Stearin is harder and burns longer than unrefined tallow. This breakthrough meant that it was possible to make tallow candles that would not produce the usual smoke and rancid odor. Stearins were also derived from palm oils, so vegetable waxes as well as animal fats could be used to make candles…
Which of the following can be inferred from paragraph 1 about candles before the nineteenth century?
(A)They did not smoke when they were burned.
(B)They produced a pleasant odor as they burned.
(C)They were not available to all.
(D)They contained sulfuric acid.
问题中的infer表明这是一道推理题。同时，问题中的 before the nineteenth century 表明问题要求我们在原文中寻找对比关系(关于这一点，见p )。 文章第一句指出：19世纪涌现的一些新发明和发现使蜡烛业发生了一场革命，这场革命使得所有人都能用蜡烛照明。 这等于说，在19世纪蜡烛业发生革命以前，并不是所有人都能用蜡烛照明，C选项表达了此意，为正确答案。
例五(句子插入题)
The Psychodynamic Approach. Theorists adopting the psychodynamic approach hold that inner conflicts are crucial for understanding human behavior, including aggression. Sigmund Freud, for example, believed that aggressive impulses are inevitable reactions to the frustrations of daily life. Children normally desire to vent aggressive impulses on other people, including their parents, because even the most attentive parents cannot gratify all of their demand immediately. ■Yet children, also fearing their parents’ punishment and the loss of parental love, come to repress most aggressive impulses. ■The Freudian perspective, in a sense, sees us as “steam engines.” ■By holding in rather than venting “steam,” we set the stage for future explosions. ■Pent-up aggressive impulses demand outlet. They may be expressed 8toward parents in indirect ways such as destroying furniture, or they may be expressed toward strangers later in life.
Look at the four squares [■] that indicate where the following sentence can be added to the passage.
According to Freud, however, impulses that have been repressed continue to exist and demand expression.
Where would the sentence best fit?
待插入句中的信号词however表明这个句子与前一句成对比关系，也就是意思上发生了转折。专有名词Freud与名词词组impulses that have been repressed也是线索，就是说待插入处的前后句必须出现这两组核心词。
阅读四个方块前后的句子，发现只有第二个方块前的句子中谈到了repress…impulses这一核心词组，而且意思与待插入句相反，因为它说的是“压抑冲动”，而待插入句说的是“冲动继续存在”。
将待插入句插入到第二个方块处，它以重复核心词组repress…impulses的方式与方块前的句子相衔接。而且，二者之间意思上的转折也与信号词however所体现的逻辑关系相符。此外，下一句中的形容词Freudian也与待插入句中的专有名词Freud相呼应。由此可见，第二个方块处是插入句子的合适位置。
亲，看到了一旦掌握对比关系这把宝剑，我们独孤求败的感觉吗?除了上述给出的几种题型的例子，几乎其他所有的托福阅读题型都涉及对比关系。对比关系是托福阅读中最常见的逻辑关系之一，如果把与之类似的比较关系也归入对比关系，那么对比关系在托福阅读中所占的比重就更大了。
如上所述，假如能增强自己对于文章中和问题中对比关系的敏感度，就能在理解文章和做题的时候，既保证正确率，又能大幅提升速度。对于上述其他几种常见逻辑关系的把握也是如此。所以，对托福阅读中逻辑关系的把握再怎么强调也不为过。
名师简介：李传伟 哈佛大学硕士，剑桥大学硕士，哈佛大学博士候选人。英语副教授、北京市优秀青年骨干教师。多年来讲授SAT阅读与写作、TOEFL阅读与写作、GRE阅读与写作等课程。主要著作有：《新托福阅读高分策略》(高等教育出版社)、《新托福写作高分策略》(高等教育出版社)、《新托福口语高分策略》(高等教育出版社)、《GRE全真试题20套》(中国第一套大型GRE试题集，为主持人和主要编写者之一，世界知识出版社)。
(摘自《新托福阅读7天突破》，李传伟编著， 中国对外翻译出版公司出版)
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