句子插入题是托福阅读十大题型之一，从句子层面考察考生对句间逻辑关系、段落大意的理解和把握。这类题目是给出一句话让我们来判断这句话应加入一个段落中四个方块的哪个部分,用鼠标双击所选的黑色方块即可。做这类题目的关键首先是理解该句子，寻找其中的衔接词，分析这个句子的特点和其在文中的作用，然后把这个句子带入原文中检验其是否合适。
掌握衔接词对解答这类问题非常重要，因为它是理解上下文和这个句子的逻辑关系的核心。衔接词语主要包括代词(指示代词，例如this, these their, it, such, another ，这些通常是上文提到过的，所以可以采用就近原则来做。);关键同义词，重复出现的形容词，副词和名词;表示因果，转折等关系的过渡词语：如，therefore, so, however, as a result, consequently, on the contrary, however 等;递进扩展词：如，furthermore, also, as well, too, in addition, moreover, besides, even, additionally等;结构配对词：如，on the one hand…. on the other hand，some…others，同时还要注意一些表示顺序的词，如first ,second ,third等。
我们来具体来一个例子：1. But there is also another special kind of conversational flow among Southern women that contributed to their writing. 2. Some of their talk took the form of tales and vignettes told for their own sake.3. Sometimes humorous, sometimes sad; all were as bright as the figures in the fine needlepoint. 4.
Look at the four positions that indicate where the following sentences can be added to the …paragraph of the passage.
These tales included grotesque, comic, and poetic descriptions, character sketches, narratives, gusts of feeling, delicate ironies, and astute observations.
Click on a position to add the sentence to the passage.
A: position 1 B: Position 2 C: Position 3 D: Position 4
接下来再来看看如何解答这道题。理解要插入的句子，These tales included grotesque, comic, and poetic descriptions, character sketches, and narratives, gusts of feeling, delicate ironies, and astute observations. 我们看这个句子是主、谓、宾结构，其中宾语为一些列的并列名词和短语。寻找衔接词，这个句子的衔接词为：These tales。分析这个句子和上下文的关系：位置1 不可能，因为它后面的句子是一个主题型句子，即，提出论点，而我们要插入的句子为一个小点，属于论据。然后看位置2，这里出现了和我们要加入句子一样的信息点Some of their talk took the form of tales and vignettes told for their own sake。显然句子放在位置2是不行的;位置3后面的句子是对其前面句子for their own sake的进一步解释。所以最后只能是位置4了。把这个句带入各个位置。检查每个位置，位置4是最恰当的。
句子插入题的一个本质和一个原则往往被大家忽略，导致失分很多。一个本质---插入句是一句“可有可无”的话。题的出题位置大家比较清楚，一般处于倒数第二题的位置，并且用来出题的段落是大家应该在前面的题目中已经见到过，而之前的题目和文章既然大家理解起来没有出现大的障碍，就说明插入进来的句子是一句可有可无的话。这就要从两个方面来理解了。
何为“可有”?既然插入句能放进原文中去，就说明它和原文是有一定关系的，所以叫“可有”，这也就意味着，插入句的部分含义是在原文中有所重复的。所以我们的重点是回到文中找那部分被重复的句意。例如：
█Watt's steam engine soon showed what it could do. █It liberated industry fromdependence on running water. █The engine eliminated water in the mines by drivingefficient pumps, which m-ade possible deeper and deeper mining. █The ready availability ofcoal inspired William Murdoch during the 1790s to develop the first new form of nighttimeillumination to be discovered in a mill-ennium and a half. Coal gas rivaled smoky oil lamps andflickering candles, a-nd early in the new century, well-to-do Londoners grew accustomed togaslit houses and even streets. Iron manufacturers, which had starved for fuel while dependingon charcoal, also benefited from ever-increasing supplies of coal: b-last furnaces with steam-powered bellows turned out more iron and steel for the new machinery. Steam became themotive force of the Industrial Revolu-tion as coal and iron ore were the raw materials.
(TPO6-Powering the Industrial Revolution)
Look at the four squares [█] that indicate where the following sentence coul-d be added tothe passage.
The factories did not have to go to the streams when power could come to th-e factories.
Where would the sentence best fit?
在上题中，“liberated industry from dependence on running water”和 “The factories did not have to go to the streams”句意便发生了重合。所以我们可以确定，文中第二句话的前后应该是我们可以选择的范围。
何为“可无”?这个便是经常被大家忽略的地方。既然这句话，可以省略，那么这个插入句究竟要符合什么特点呢?还是以上题为例，我们发现 “liberated industry from dependence on running water”和 “The factories didnot have to go to the streams”句意发生了重合，那究竟应该把插入句放在第二个█还是第三个█呢?这时就需要分情况讨论了：
情况1：放在第二个█，也就是说我们认为插入句是和下文有关系，既然要符合“可无”这个本质，所以说插入句必须是对下文概括或者引出。
情况2：放在第三个█，也就是说我们认为插入句是和上文有关系，既然要符合“可无”这个本质，所以说插入句必须是对上文进一步解释。
综合以上两种情况，我们会发现，插入句要么总结引出下文，要么进一步解释上文。所以我们会发现，在插入题中，前一句的叙述范围应该总比后一句大。 根据上述内容，也就引出了我们需要注意的一个非常重要的做题原则。
一个原则。在插入题中，句子的叙述顺序遵循从大到小，从抽象到具体的原则。找到重复的句意后，按照大小顺序安置插入句的位置。在上题中，“liberated industry from dependence on running water”的意思是解放了工厂对水流的依赖。 “The factories did not have to go to the streams”的意思是工厂不用去往河流的位置。显然前者说得更概括和抽象，后者更具体，所以按照从大到小的顺序，应该选择第二个█。
