句子插入題是托福閱讀十大題型之一，從句子層面考察考生對句間邏輯關系、段落大意的理解和把握。這類題目是給出一句話讓我們來判斷這句話應加入一個段落中四個方塊的哪個部分,用鼠標雙擊所選的黑色方塊即可。做這類題目的關鍵首先是理解該句子，尋找其中的銜接詞，分析這個句子的特點和其在文中的作用，然后把這個句子帶入原文中檢驗其是否合適。
掌握銜接詞對解答這類問題非常重要，因為它是理解上下文和這個句子的邏輯關系的核心。銜接詞語主要包括代詞(指示代詞，例如this, these their, it, such, another ，這些通常是上文提到過的，所以可以采用就近原則來做。);關鍵同義詞，重復出現的形容詞，副詞和名詞;表示因果，轉折等關系的過渡詞語：如，therefore, so, however, as a result, consequently, on the contrary, however 等;遞進擴展詞：如，furthermore, also, as well, too, in addition, moreover, besides, even, additionally等;結構配對詞：如，on the one hand…. on the other hand，some…others，同時還要注意一些表示順序的詞，如first ,second ,third等。
我們來具體來一個例子：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
接下來再來看看如何解答這道題。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. 我們看這個句子是主、謂、賓結構，其中賓語為一些列的并列名詞和短語。尋找銜接詞，這個句子的銜接詞為：These tales。分析這個句子和上下文的關系：位置1 不可能，因為它后面的句子是一個主題型句子，即，提出論點，而我們要插入的句子為一個小點，屬于論據。然后看位置2，這里出現了和我們要加入句子一樣的信息點Some of their talk took the form of tales and vignettes told for their own sake。顯然句子放在位置2是不行的;位置3后面的句子是對其前面句子for their own sake的進一步解釋。所以最后只能是位置4了。把這個句帶入各個位置。檢查每個位置，位置4是最恰當的。
句子插入題的一個本質和一個原則往往被大家忽略，導致失分很多。一個本質---插入句是一句“可有可無”的話。題的出題位置大家比較清楚，一般處于倒數第二題的位置，并且用來出題的段落是大家應該在前面的題目中已經見到過，而之前的題目和文章既然大家理解起來沒有出現大的障礙，就說明插入進來的句子是一句可有可無的話。這就要從兩個方面來理解了。
何為“可有”?既然插入句能放進原文中去，就說明它和原文是有一定關系的，所以叫“可有”，這也就意味著，插入句的部分含義是在原文中有所重復的。所以我們的重點是回到文中找那部分被重復的句意。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?
在上題中，“liberated industry from dependence on running water”和 “The factories did not have to go to the streams”句意便發生了重合。所以我們可以確定，文中第二句話的前后應該是我們可以選擇的范圍。
何為“可無”?這個便是經常被大家忽略的地方。既然這句話，可以省略，那么這個插入句究竟要符合什么特點呢?還是以上題為例，我們發現 “liberated industry from dependence on running water”和 “The factories didnot have to go to the streams”句意發生了重合，那究竟應該把插入句放在第二個█還是第三個█呢?這時就需要分情況討論了：
情況1：放在第二個█，也就是說我們認為插入句是和下文有關系，既然要符合“可無”這個本質，所以說插入句必須是對下文概括或者引出。
情況2：放在第三個█，也就是說我們認為插入句是和上文有關系，既然要符合“可無”這個本質，所以說插入句必須是對上文進一步解釋。
綜合以上兩種情況，我們會發現，插入句要么總結引出下文，要么進一步解釋上文。所以我們會發現，在插入題中，前一句的敘述范圍應該總比后一句大?！「鶕鲜鰞热?，也就引出了我們需要注意的一個非常重要的做題原則。
一個原則。在插入題中，句子的敘述順序遵循從大到小，從抽象到具體的原則。找到重復的句意后，按照大小順序安置插入句的位置。在上題中，“liberated industry from dependence on running water”的意思是解放了工廠對水流的依賴。 “The factories did not have to go to the streams”的意思是工廠不用去往河流的位置。顯然前者說得更概括和抽象，后者更具體，所以按照從大到小的順序，應該選擇第二個█。
