在托福閱讀考試過程中，遇到閱讀插入句的題目，有種被前後夾攻的感覺。複雜的邏輯關係常常讓考生們就這麼失分了。相信有學生也會將選項放入句中後去讀一讀順不順，除非你英文語感很好不然其實有點浪費時間囉。
- 仔細閱讀插入句，理解句意
- 根據句子內的關鍵詞，推斷插入位置前後可能出現的內容
- 檢查語意是否流暢，符合文章邏輯
- 找關鍵詞（代詞、邏輯詞、訊息重複的話題、或者同義詞改寫）
訊息重複的話題
【Firn has the appearance of wet sugar, but it is almost as hard as ice.】
Where would the sentence best fit?
Glaciers are slowly moving masses of ice that have accumulated on land in areas where more snowfalls during a year than melts. Snow falls as hexagonal crystals, but once on the ground, snow is soon transformed into a compacted mass of smaller, rounded grains.█As the air space around them is lessened by compaction and melting, the grains become denser. █With further melting, refreezing, and increased weight from newer snowfall above, the snow reaches a granular recrystallized stage intermediate between flakes and ice known as firn. █With additional time, pressure, and refrozen melt water from above, the small firn granules become larger, interlocked crystals of blue glacial ice. █When the ice is thick enough, usually over 30 meters, the weight of the snow and firn will cause the ice crystals toward the bottom to become plastic and to flow outward or downward from the area of snow accumulation.
Ø可以先在文章中找到與插入句相同的字Firn，但按照邏輯，應該是先說firn的形成過程，再描述插入句中的Firn是什麼樣，所以灰底白字是誤區，正確答案是第三個【█】才對。
插入句出現代詞開頭 （this、they、it、these）
At times, it is actually possible to watch the effects of natural selection in host-parasite relationships. For example, Australia during the 1940 s was overrun by hundreds of millions of European rabbits. █ The rabbits destroyed huge expanses of Australia and threatened the sheep and cattle industries. █ In 1950, myxoma virus, a parasite that affects rabbits, was deliberately introduced into Australia to control the rabbit population. █ Spread rapidly by mosquitoes, the virus devastated the rabbit population. █ The virus was less deadly to the offspring of surviving rabbits, however, and it caused less and less harm over the years. Apparently, genotypes (the genetic make-up of an organism) in the rabbit population were selected that were better able to resist the parasite. Meanwhile, the deadliest strains of the virus perished with their hosts as natural selection favored strains that could infect hosts but not kill them. Thus, natural selection stabilized this host-parasite relationship.
【This massive population began a century earlier as a mere twelve pairs of imported rabbits that reproduced quickly and developed into a major problem.】
Ø在每個空之前找是否有他們的指代物件，有的，就是正確的。插入句的this massive(大規模的) population所指的對象符合第一個【█】前句子提到的 hundreds of millions of European rabbits
插入句出現邏輯關係詞（however、but、therefore、also、then等）
【To better understand breathing during sleep, it is, however, helpful to first understand how respiration works in general.】
Of all the physiological differences in human sleep compared with wakefulness that have been discovered in the last decade, changes in respiratory control are most dramatic. Not only are there differences in the level of the functioning of respiratory systems, there are even changes in how they function. Movements of the rib cage for breathing are reduced during sleep, making the contractions of the diaphragm more important. . █ Yet because of the physics of lying down, the stomach applies weight against the diaphragm and makes it more difficult for the diaphragm to do its job. █ However, there are many other changes that affect respiration when asleep.
█ During wakefulness, breathing is controlled by two interacting systems. █The first is an automatic, metabolic system whose control is centered in the brain stem. It subconsciously adjusts breathing rate and depth in order to regulate the levels of carbon dioxide (CO2) and oxygen (O2), and the acid-base ratio in the blood. The second system is the voluntary, behavioral system. Its control center is based in the forebrain, and it regulates breathing for use in speech, singing, sighing, and so on. It is capable of ignoring or overriding the automatic, metabolic system and produces an irregular pattern of breathing.
Ø插入句出現however，表示本句為轉折句。
轉折句出現表示前後文應該出現論述重點的不同。
根據插入句的句意，可以推斷出本句具有明顯引起下文所述的“平時是如何呼吸的，”承接上文論述的“睡眠中的呼吸” ，第三個【█】。
插入句出現邏輯關係詞（however、but、therefore、also、then等）
【Therefore, if the paintings were connected with hunting, some other explanation is needed. 】
Another explanation for the focus on animals might be that these people sought to improve their luck at hunting. █This theory is suggested by evidence of chips in the painted figures, perhaps made by spears thrown at the drawings. █But if improving their hunting luck was the chief motivation for the paintings, it is difficult to explain why only a few show signs of having been speared. █Perhaps the paintings were inspired by the need to increase the supply of animals. Cave art seems to have reached a peak toward the end of the Upper Paleolithic period, when the herds of game were decreasing. █
Ø插入句出現therefore，表示前後文承接因果關係。
根據插入句的句意，第三個【█】其前面在講壁畫主要動機是提高打獵命中率，後面在講壁畫或許是出於增加獵物的需求而畫的畫。
延伸文章：TOEFL三戰90分心得分享
托福閱讀如何從23分進步到27分
訊息重複的話題
