在托福阅读考试中，长难句在考试中最直接的运用就是考察插入句子题和解释句子题。对于这样的题目，我们在不能读懂句子的情况下，能够把握的就是句子的内在关系，即逻辑。逻辑在解释句子题中的运用尤为重要，以前有学生反映，在考试中其实句子根本就不能读懂，而利用逻辑就能迅速排除选项，从而找到正确的答案。所以说，逻辑是我们托福阅读中的隐形解题帮手，考生们一定要尤为关注。

　　下面是托福阅读中经常出现的四大逻辑关系，把握了它们就等于掌握了托福阅读解题技巧的一个重要部分。

　　1. 因果关系

　　因：because, because of, for, as, since, in that, on account of, with

　　果：so, so that, therefore, thereby, as a result, hence, thus, consequently, accordingly

　　因果关系除了传统意义上的显性因果表达词外，隐性的因果同样是不可忽略的一个重要部分。

　　隐性因果：

　　A 导致(因-果)：cause, reason, lead to, give rise to, result in, render, make, let, ask, support, push, stimulate, spark, spur, fuel, produce, be responsible for

　　如The increased pressures of expanding populations have led to the removal of woody plants so that many cities and towns are surrounded by large areas completely lacking in trees and shrubs。

　　在这段话中，有lead to, 表示了导致的意思，即结果;而so that 更进一步表示了后面的结果，所以可以充分判定这段话有因果关系的逻辑。

　　B 由…而来(果-因)：result from, derive from, originate from, initiate from, stem from, be responsive to, be attributable to

　　如 “The extreme seriousness of desertification results from the vast areas of land and tremendous numbers of people affected, as well as from the great difficulty of reversing or even slowing the process。”

　　在这段话中，根据result from可以推断出有因果关系，那如果是解释句子题时，选项中有因果关系就可以优先考虑。

　　C 反映，体现(果-因)： reflect, present, demonstrate, suggest, imply, show

　　This result demonstrates that…

　　D 考虑到： given, considering, in view of, thanks to, according to

　　He succeeded thanks to (in view of) his effort.

　　E 依赖于： rely on, depend on, resort to,

　　He resorted to books when he had problems.

　　F 条件关系：when, once, as soon as, as long as

　　As soon as he got the money, he would leave the country at once.

　　G 分词短语，不定式做状语

　　Failing in the final exam, she cried.

　　2. 对比转折关系

　　A 对比：while, whereas, on the other hand

　　在解释句子题，插入句子题中，一旦出现对比关系，学生在掌握的基础上就能非常快速的判定句间和句内的关系。While, whereas 前后连接的是平行结构，on the other hand前必定有on one hand, 可以用来把握句间关系。

　　B 转折：but, although, despite, in spite of, nevertheless, however

　　转折是托福阅读的一个经典考点之一，掌握这些转折词对考试非常有帮助。

　　3. 比较关系

　　A 同级比较 as…as

　　B 比较级：more…than, -er than, less…than

　　C 变化：change, alter, vary, modify, revise, increase, decrease, enhance, diminish, develop, progress, advance, improve, retreat, degenerate, continue, remain

　　D 差异：different, distinguish, separate, same, similar, comparable, compare…to