插入文本题是托福阅读十大类题型中的必考题型，每篇文章出现一道，考查方式如下所示：

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.■Very exciting discoveries have finally allowed scientists to reconstruct the most likely origins of cetaceans. ■In 1979, a team looking for fossils in northern Pakistan found what proved to be the oldest fossil whale.

Look at the four squares [■] that indicate where the following sentence can be added to the passage.
This is a question that has puzzled scientists for ages.
Where would the sentence best fit?
（该例题选自新托福考试官方指南第三版The origins of Cetaceans P64）

    这类题型给出一个或两个段落，段落中有四个方框代表备选位置，再给出一句待插入的句子，问这个句子放置在文中的哪个空格处最合适。

    这类题型通常情况出现在倒数第二题的位置，很多考生由于做到接近结尾的时候往往时间紧迫，因此没有对题型进行充分的思考，导致该类题型失分率较高。而事实上，这种题型属于规律性非常强的题型，尽管对于考生理解和掌握文章的整体性和衔接性提出了较高的要求，但是倘若能掌握好这类题型的解题思路，应该也是能做到迎刃而解的。

    解这类题型最重要的原则是“承上启下”，即插入句子放置到原文后能起到“承上启下”的作用，具体而言，判断“承上启下”有以下三种方法：

    、    词汇复现原则。若是插入句子中有this/these + 名词，则到文章中去寻找该名词，若只有一处出现，则放置在文中这个名词之后即可。这是因为凡是this, these后面出现的名词，一定是前文中出现过，且不会隔出现的地方太远，这便是词汇复现，即重复出现。这和中文的逻辑也是一样的。

例：（此题选自Which Hand Did They Use?   TPO 12）
We all know that many more people today are right-handed than left-handed. Can one trace this same pattern far back in prehistory? ■Much of the evidence about right-hand versus left-hand dominance comes from stencils and prints found in rock shelters in Australia and elsewhere, and in many Ice Age caves in France, Spain, and Tasmania. ■When a left hand has been stenciled, this implies that the artist was right-handed, and vice versa. ■Even though the paint was often sprayed on by mouth, one can assume that the dominant hand assisted in the operation. One also has to make the assumption that hands were stenciled palm downward—a left hand stenciled palm upward might of course look as if it were a right hand. ■Of 158 stencils in the French cave of Gargas, 136 have been identified as left, and only 22 as right; right-handedness was therefore heavily predominant.

Look at the four squares [■] that indicate where the following sentence could be added to the passage.
The stencils of hands found in these shelters and caves allow us to draw conclusions about which hand was dominant.
Where would the sentence best fit?

    插入句出现“these shelters”，文章中只有第二个方框前一处出现shelters，因此直接放置在第二空即可。

    当然，讲到此处，学生们通常会有疑问，如果文中多处出现这个名词该怎么办？自然我们就不能直接选出答案，但至少可以将没有出现该名词的选项排除。另外，this/these + 名词，这里的名词也有可能出现变体，或者称之为同义替换。

    例：（此题选自Petroleum Resources    TPO4）
Continued sedimentation—the process of deposits' settling on the sea bottom—buries the organic matter and subjects it to higher temperatures and pressures, which convert the organic matter to oil and gas. █As muddy sediments are pressed together, the gas and small droplets of oil may be squeezed out of the mud and may move into sandy layers nearby. █Over long periods of time (millions of years), accumulations of gas and oil can collect in the sandy layers. █Both oil and gas are less dense than water, so they generally tend to rise upward through water-saturated rock and sediment. █

Look at the four squares [█] that indicate where the following sentence could be added to the passage.
Unless something acts to halt this migration, these natural resources will eventually reach the surface.
Where would the sentence best fit?

    插入句出现了“this migration”，和“these natural resources”，后者并不能成为一个很好的判断，因为这里的“自然资源”显然是指“gas and oil”，但是文中四个方框前都有“gas and oil”，因此，就不能根据“these natural resources”来判断了。那么，从“this migration”切入。但是原文中却没有出现migration这个词，migration意思为“迁徙，迁移”，在特定语境中也可表示“移动”，因此文中有两处可以成为它的同义替换，一个是第二空之前的move，另一个是第四空之前的rise，因此空和第三空基本可以排除。再从意思上来看，插入句的意思为“除非有某事物阻止了这个移动，不然这些自然资源就会最终到达表面”。不然分析出，在海底的什么动作行为，若不加阻止，便会到达表面：显然是上升（rise），而不是一般的移动（move）。因此答案选择D。


    第二、    逻辑呼应原则。在有些插入句子中，并没有出现this/these这样的词汇复现标志词，但是却出现了consequently, under different climatic conditions, in fact, indeed这样的逻辑关联词，考生们一定要敏锐的发现这些关联词所暗示的上下文之间的关系。

例：（此题选自Geology and Landscape   OG第三版 P255）
Under very cold conditions, rocks can be shattered by ice and frost. Glaciers may form in permanently cold areas, and these slowly moving masses of ice cut out valleys, carrying with them huge quantities of eroded rock debris. █In dry areas the wind is the principal agent of erosion. █It carries fine particles of sand, which bombard exposed rock surfaces, thereby wearing them into yet more sand. █Even living things contribute to the formation of landscapes. █Tree roots force their way into cracks in rocks and, in so doing, speed their splitting. In contrast, the roots of grasses and other small plants may help to hold loose soil fragments together, thereby helping to prevent erosion by the wind.
Look at the four squares [■] that indicate where the following sentence could be added to the passage.
Under different climatic conditions, another type of destructive force contributes to erosion.
Where would the sentence best fit?

    由于插入句以Under different climatic conditions（在不同的气候条件下）作为开始，因此在它前面一定要有under…conditions（在某种气候条件下）。原文的首句便是Under very cold conditions，因此有同学直接将答案放置在个空格。事实上，尽管针对这道题答案选对了，但是推理却还不是非常严谨。根据上述推理，只能判断出，插入句应放置在文中句话之后，但是是否是紧挨着它，还是放置在更加往后的空格却是不能确定的。进一步的推理是：插入句的意思“在其他气候条件下，另一种摧毁性的力量促进了腐蚀”。原文中句，在非常寒冷的气候条件下，提及到的摧毁性的力量是冰和霜冻，若空后面依然在说冰和霜冻，则不能放置在空。但是空后却在说风这种力量了，这是相对于冰和霜冻的另一种摧毁性的力量，因此，需要将插入句放置在个空格。

    第三、    排除法。以上两种方式属于直接选取正确答案的方式，有的适合直接选取答案不是非常有效，排除法却非常有效。所谓排除法是指，若是某个空格前后衔接非常紧密，那么这个空格不能再插入句子，应该被排除。所以前后衔接紧密可以通过指代关系、词汇复现等方式来判断。

    例：（此题选自Biological Clocks    TPO13）
Animals need natural periodic signals like sunrise to maintain a cycle whose period is precisely 24 hours. ■Such an external cue not only coordinates an animal's daily rhythms with particular features of the local solar day but also—because it normally does so day after day-seems to keep the internal clock's period close to that of Earth's rotation. ■Yet despite this synchronization of the period of the internal cycle, the animal's timer itself continues to have its own genetically built-in period close to, but different from, 24 hours. ■Without the external cue, the difference accumulates and so the internally regulated activities of the biological day drift continuously, like the tides, in relation to the solar day. ■This drift has been studied extensively in many animals and in biological activities ranging from the hatching of fruit fly eggs to wheel running by squirrels. Light has a predominating influence in setting the clock. Even a fifteen-minute burst of light in otherwise sustained darkness can reset an animal's circadian rhythm. Normally, internal rhythms are kept in step by regular environmental cycles. For instance, if a homing pigeon is to navigate with its Sun compass, its clock must be properly set by cues provided by the daylight/darkness cycle.

Look at the four squares [■] that indicate where the following sentence could be added to the passage.
Because the internal signals that regulate waking and going to sleep tend to align themselves with these external cues, the external clock appears to dominate the internal clock.
Where would the sentence best fit?

    此题若直接选择有一些困难，但若用排除法却很好解。第四空后面有“This drift”，第四空前面出现了drift，但是插入句中却没有drift，因此第四空前后衔接紧密，不能再插入句子，排除。同样的道理，第三空后面有“the difference”，第三空之前有“but different from”，插入句却没有谈到“different”的问题，因此也应被排除。若是考生对于前面考过的指代题有所印象，不难判断出空后面的“Such an external cue”指的是前一句的“sunrise”（此处不详述前文的指代题），因此空也被排除，答案是第二空。

    综上，插入文本题是一种规律性很强的题型，只要掌握了正确的解题思路，一定能做对这种题型。

    ，希望考生们能掌握正确的做题思路，提升英语基本功，实现托福高分的梦想。

作者简介：北京新航道学校托福阅读、SAT词汇填空主讲。北京语言大学英语语言文学学士，对外经济贸易大学经济学硕士。具有丰富的英语教学与测试研究经验，以极具亲和力的教学风格见长。

(本文选自新航道《托福频道》2012年上半年刊)