句子插入題本來是屬于托福閱讀10種題型中比較簡單的類型，但是許多同學都會因為缺乏對題型考點的認識以及對句子插入題一個本質和一個原則的忽略而導致失分很多。下面小編就來為大家具體講解托福閱讀句子插入題的本質和原則。
托福閱讀句子插入題本質：插入句“可有可無”
本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.
(托福官方真題6-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。
根據上述內容，也就引出了我們需要注意的一個非常重要的做題原則：
托福閱讀句子插入題原則介紹
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█。
托福閱讀句子插入題本質原則實例講解
Trade between the West and the settled and prosperous Chinese dynasties introduced newforms and different technologies. One of the most far-reaching e-xamples is the impact of thefine ninth-century AD. Chinese porcelain ware-s imported into the Arab world. █So admiredwere these pieces that they encouraged the development of earthenware made in imitation ofporcelain and instigated research into the meth-od of their manufacture. █From the MiddleEast the Chinese acquired a blue pigment—a purified form of cobalt oxide unobtainable atthat time in China—that contained only a low l-evel of manganese. Cobalt ores found in Chinahave a high manganese conte-nt, which produces a more muted blue-gray color. █In theseventeenth century, the trading activities of the Dutch East India Com-pany resulted in vastquantities of decorated Chinese porcelain being brough-t to Europe, which stimulated andinfluenced the work of a wide variety of wares, notably Delft. █The Chinese themselvesadapted many specific vessel forms from the West, such as bottles with long spouts, anddesigned a range of decorative pattern-s especially for the European market.
(托福官方真題10-Chinese Pottery)
Look at the four squares [█]that indicate where the following sentence could be added tothe passage.
Foreign trade was also responsible for certain innovations in coloring.
Where could the sentence best fit?
在上題中，我們發現，插入句的“certain innovations in coloring”與原文中的“the Chinese acquired a blue pigment”句意進行了重復，顯然，插入句說得更概括，范圍更大，所以根據從大到小的原則，應該選擇第二個█。
以上就是托福閱讀句子插入題的本質和原則介紹，解答這一題型有困難的同學趕緊學起來。
