【实例解析】托福阅读句子插入题-Savanna Formation
托福阅读句子插入题解析-小申托福
托福阅读句子插入题解析作为托福阅读十大题型之一，句子插入题一般每篇文章会出现一个。
句子插入题题目形式固定，一般表现为如下形式：Look at the four squares ■ that indicate where the following sentence could be added to the passage.This economic reliance on livestock in certain regions makes large tracts of land susceptible to overgrazing.Where does the sentence best fit?■The raising of livestock is a major economic activity in semiarid lands, where grasses are generally the dominant type of natural vegetation. ■The consequences of an excessive number of livestock grazing in an area are the reduction of the vegetation cover and the trampling and pulverization of the soil. ■This is usually followed by the drying of the soil and accelerated erosion. ■可以看到，在句子插入题中，会给出一段文字，文字里有四个小黑框，然后会给出一个加粗的句子，问这个加粗的句子放入到四个小黑框的哪一个是最合适的。
不少同学由于以前没有接触过类似的题型，觉得句子插入题很棘手。
其实只要我们掌握正确的解题思路，句子插入题是可以又快又准确地完成的。
托福阅读之插入题-
托福阅读之插入题插入题重点考察英语句子间的逻辑语义关系,即英文句子是如何衔接在一起的,如果掌握了句子间的衔接手法,这种问题就迎刃而解了。
首位衔接法认真阅读要插入的句子,找出题干句子中的关键词。
关键词一般是名词或代词,在句子中做主语或者是宾语,一般指代插入句子的前面主语或是宾语,是后面那个句子中的某个名词或同义词,即同义词复现原则。
最后一定要再读一遍,看放入文章中是否符合逻辑要求例:《新托福阅读金牌教程》P 81 passage 3“Having evolved to live in the d esert, pack rats consume little water so their urine is particularly thick.”这句话的主语为pack rats, 而A后面那句首次出现了pack rats,B后的句子“Once the urine is secreted and dries···”,主语为the urine, 证明前面一句有提到urine,综上,此句应该放在B,即:In order to stabilize the structure, the pack rat urinates in the midden debris. Having evolved to live in the desert, pack rats consume little water so their urine is particularly thick. Once the urine is secreted and dries, it crystallizes into a deep, reddish-brown viscous coating called amberat.逻辑关系法;利用过渡词和代词,确定上下文语义逻辑关系1.指代关系:具体包括人称代词、指示代词和关系代词等。
托福阅读句子插入题实例剖析
句中出现“also”，根据句意，可以推测正确位置之前至少会提到与动物相关的某种特性，所以才会紧跟插入句所说的“also有雄性O动物的call”。发现第二个位置前面提到rhinoceros hornbill的叫声cries和gibbons的喊声calls，那么把插入句放到第二个位置，起到了进一步举例说明的作用，满足了also的关系，前后逻辑严谨。
例题2
题目出现however，表示本句为转折句。转折句出现表示前后文应该出现论述重点的不同，较多出现的情况为后文反驳前文，较少出现的情况也会表示后文开始论述与前文不完全相同的另一个内容。
根据插入句的句意“然而，为了更好理解睡眠中的呼吸，先搞清楚平时是如何呼吸是很有帮助的”，可以推断出本句具有明显的承上启下的作用，承接上文论述的“睡眠中的呼吸”，引起下文所述的“平时是如何呼吸的”。根据推断寻找后，发现C位置符合承上启下的关系，即为正确答案。
例题如下：
句中出现代词“this period”，插入位置前面必然提到某一个时期。同时，我们还要注意，句子还提到，这个时期里Sweden和Denmark经济发展特别好。
原文前三个位置之前的句子都提到了时期，分别是18世纪、19世纪上半叶和19世纪下半叶。然而前两句话所说的时期中，Sweden和Denmark都是处在落后的位置。而第三句话however转折之后的信息提到，19世纪下半叶，尤其是最后二三十年，它们(指的是Netherlands、Denmark、Norway和Sweden)发展特别快。也就是说，19世纪下半叶才是插入句中this period指代的内容，前两个时期都不能复合指代内容的特性。所以C是正确答案。
误区三：托福阅读文章和题目关系界定
在托福阅读中，文章是基础，但很多考生认为托福阅读题目要比文章重要。这表现在考生在托福阅读备考中常常会极力寻找关于题目解答和应试的技巧而并没有注意文章的重要性。其实很多时候是因为文章没有读懂而答不对题目，而不是因为不会答题而答不对题。所以要重视文章，在文章理解中注意猜词，尽量理解透彻;从整体上看文章，而不是只关注对题目有帮助的文章部分，考生往往因为只是从小范围看文章，只针对题目理解文章，对文章的理解常常是支离破碎没有全局概念的。这样极容易答不对最后一个大题，对文章的理解也是有问题的。
托福阅读 31-3 Savanna Formation
Savanna Formation1.Located in tropical areas at low altitudes, savannas are stable ecosystems, some wet and some dry consisting of vast grasslands with scattered trees and shrubs. They occur on a wide range of soil types and in extremes of climate. There is no simple or single factor that determines if a given site will be a savanna, but some factors seem to play important roles in their formation.2.Savannas typically experience a rather prolonged dry season. One theory behind savanna formation is that wet forest species are unable to withstand the dry season, and thus savanna, rather than rain forest, is favored on the site. Savannas experience an annual rainfall of between 1,000 and 2,000 millimeters, most of it falling in a five- to eight-month wet season. Though plenty of rain may fall on a savanna during the year, for at least part of the year little does, creating the drought stress ultimately favoring grasses. Such conditions prevail throughout much of northern South America and Cuba, but many Central American savannas as well as coastal areas of Brazil and the island of Trinidad do not fit this pattern. In these areas, rainfall per month exceeds that in the above definition, so other factors must contribute to savanna formation.3.In many characteristics, savanna soils are similar to those of some rain forests, though more extreme. For example, savanna soils, like many rain forest soils, are typically oxisols (dominated by certain oxide minerals) and ultisols (soils containing no calcium carbonate), with a high acidity and notably low concentrations of such minerals as phosphorus, calcium, magnesium, and potassium, while aluminum levels are high. Some savannas occur on wet, waterlogged soils; others on dry, sandy, well-drained soils. This may seem contradictory, but it only means that extreme soil conditions, either too wet or too dry for forests, are satisfactory for savannas. More moderate conditions support moist forests.4.Waterlogged soils occur in areas that are flat or have poor drainage. These soils usually contain large amounts of clay and easily become water saturated. Air cannot penetrate between the soil particles, making the soil oxygen-poor. By contrast, dry soils are sandy and porous, their coarse textures permitting water to drain rapidly. Sandy soils are prone to the leaching of nutrients and minerals and so tend to be nutritionally poor. Though most savannas are found on sites with poor soils (because of either moisture conditions or nutrient levels of both), poor soils can and do support lush rain forest.5.Most savannas probably experience mild fires frequently and major burns every two years or so. Many savanna and dry-forest plant species are called pyrophytes, meaning they are adapted in various ways to withstand occasional burning. Frequent fire is a factor to which rain forest species seem unable to adapt, although ancient charcoal remains from Amazon forest soils dating prior to the arrival of humans suggest that moist forests also occasionally burn. Experiments suggest that if fire did not occur in savannas in the Americas, species composition would change significantly. When burning occurs, it prevents competition among plant species from progressing to the point where some species exclude others, reducing the overall diversity of the ecosystem. But in experimental areas protected from fire, a few perennial grass species eventually come to dominate, outcompeting all others. Evidence from other studies suggests that exclusion of fire results in markedly decreased plant-species richness, often with an increase in tree density. There is generally little doubt that fire is a significant factor in maintaining savanna, certainly in most regions.6.On certain sites, particularly in South America, savanna formation seems related to frequent cutting and burning of moist forests for pastureland. Increase in pastureland and subsequent overgrazing have resulted in an expansion of savanna. The thin thin upper layer of humus (decayed organic matter) is destroyed by cutting and burning. Humus is necessary for rapid decomposition of leaves by bacteria and fungi and for recycling by surface roots. Once the humus layer disappears, nutrients cannot be recycled and leach from the soil, converting soil from fertile to infertile and making it suitable only for savanna vegetation. Forests on white, sandy soil are most susceptible to permanent alteration.1.Located in tropical areas at low altitudes, savannas are stable ecosystems, some wet and some dry consisting of vast grasslands with scattered trees and shrubs. They occur on a wide range of soil types and in extremes of climate. There is no simple or single factor that determines if a given site will be a savanna, but some factors seem to play important roles in their formation.2.Savannas typically experience a rather prolonged dry season. One theory behind savanna formation is that wet forest species are unable to withstand the dry season, and thus savanna, rather than rain forest, is favored on the site. Savannas experience an annual rainfall of between 1,000 and 2,000 millimeters, most of it falling in a five- to eight-month wet season. Though plenty of rain may fall on a savanna during the year, for at least part of the year little does, creating the drought stress ultimately favoring grasses. Such conditions prevail throughout much ofnorthern South America and Cuba, but many Central American savannas as well as coastal areas of Brazil and the island of Trinidad do not fit this pattern. In these areas, rainfall per month exceeds that in the above definition, so other factors must contribute to savanna formation.1.The word “prolonged” in the passage is closest in meaning to:o Predictableo Destructiveo Lengthyo Unproductive2.In paragraph 2, the author mentions savannas in Central America, Brazil, and theisland of Trinidad in order to:o Argue that these savannas are similar to those in South America and Cuba o Point out exceptions to the pattern of savanna formation in areas with drought stresso Provides additional examples of savannas in areas with five- to eight-month wet seasonso Indicate areas where savannas are being gradually replaced by rain forests3.In many characteristics, savanna soils are similar to those of some rain forests, though more extreme. For example, savanna soils, like many rain forest soils, are typically oxisols (dominated by certain oxide minerals) and ultisols (soils containing no calcium carbonate), with a high acidity and notably low concentrations of such minerals as phosphorus, calcium, magnesium, and potassium, while aluminum levels are high. Some savannas occur on wet, waterlogged soils; others on dry, sandy, well-drained soils. This may seem contradictory, but it only means that extreme soil conditions, either too wet or too dry for forests, are satisfactory for savannas. More moderate conditions support moist forests.3.According to paragraph 3, rain forests and savannas differ in that:o The soils in rain forests contain fewer minerals than savanna soils doo Savannas affect soil conditions more than rain forests doo Unlike rain forests, savannas prefer sandy, well-drained soils to soils that are very weto Unlike rain forests, savannas may develop under both very dry and very wet soil conditions4.The word “notably” in the passage is closest in meaning to:o Similarlyo Especiallyo Usuallyo Relatively5.According to paragraph 3, all of the following are true of savanna soils EXCEPT:o They have high concentrations of potassium.o They contain high levels of aluminum.o They are very acidic.o They contain large amounts of certain oxide minerals.4.Waterlogged soils occur in areas that are flat or have poor drainage. These soils usually contain large amounts of clay and easily become water saturated. Air cannot penetrate between the soil particles, making the soil oxygen-poor. By contrast, dry soils are sandy and porous, their coarse textures permitting water to drain rapidly. Sandy soils are prone to the leaching of nutrients and minerals and so tend to be nutritionally poor. Though most savannas are found on sites with poor soils (because of either moisture conditions or nutrient levels of both), poor soils can and do support lush rain forest.6.According to paragraph 4, which of the following is true of waterlogged soils?o Their upper layers are usually sandy and porous.o They cannot support savannas.o They contain little oxygen.o They are prone to the leaching of nutrients and minerals.7.The fact that “poor soils can and do support lush rain forest” suggests that:o Poor soils alone may not be enough to explain why an area becomes a savannao Rain forest vegetation can significantly lower the quality of soilso Drought stress is the single most important factor in savanna formationo Minerals are more important than moisture for the growth of trees5.Most savannas probably experience mild fires frequently and major burns every two years or so. Many savanna and dry-forest plant species are called pyrophytes, meaning they are adapted in various ways to withstand occasional burning. Frequent fire is a factor to which rain forest species seem unable to adapt, although ancient charcoal remains from Amazon forest soils dating prior to the arrival of humans suggest that moist forests also occasionally burn. Experiments suggest that if fire did not occur in savannas in the Americas, species composition would change significantly. When burning occurs, it prevents competition among plant species from progressing to the point where some species exclude others,reducing the overall diversity of the ecosystem. But in experimental areas protected from fire, a few perennial grass species eventually come to dominate, outcompeting all others. Evidence from other studies suggests that exclusion of fire results in markedly decreased plant-species richness, often with an increase in tree density. There is generally little doubt that fire is a significant factor in maintaining savanna, certainly in most regions.8.Which of the sentence below best expresses the essential information in thehighlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.o Rain forest species seem unable to adapt to fires created by humans.o Ancient charcoal remains suggest that, prior to the arrival of humans, fires occurred frequently in rain forests.o Ancient charcoal remains in Amazon forests suggest that rain forest species adapted to the area long before the arrival of humans.o Rain forests species appear unable to adapt to frequent fires, but evidence from the past suggests that rain forests sometimes do burn.9.The word “markedly” in the passage is closest in meaning to:o Dangerouslyo Noticeablyo Rapidlyo Gradually10.Paragraph 5 supports which of the following statements regarding theimportance of fires in maintaining savannas?o Fires prevent the growth of pyrophytes.o Fires eliminate some species and thus reduce the overall diversity of the ecosystem.o Fires that occur once every two years are unlikely to help maintain savannas.o Fires prevent some species from eliminating other species with which they compete.6.On certain sites, particularly in South America, savanna formation seems related to frequent cutting and burning of moist forests for pastureland. Increase in pastureland and subsequent overgrazing have resulted in an expansion of savanna. The thin upper layer of humus (decayed organic matter) is destroyed by cutting and burning. Humus is necessary for rapid decomposition of leaves by bacteria and fungi and for recycling by surface roots. Once the humus layer disappears, nutrients cannot be recycled and leach from the soil, converting soil from fertile to infertile andmaking it suitable only for savanna vegetation. Forests on white, sandy soil are most susceptible to permanent alteration.11.The word “subsequent” in the passage is closest in meaning to:o Expanded in areao Harmfulo Following in timeo Repeated12.According to paragraph 6, human activity affects soils in all of the following waysEXCEPT:o Decomposition of leaves occurs too fast for surface roots to obtain nutrients.o Nutrients are not recycled.o Humus is destroyed.o Certain soils become unable to support vegetation other than savanna vegetation.13.In addition, humans have contributed to the conditions favoring the formation ofsavannas.Where would the sentence best fit?7.Most savannas probably experience mild fires frequently and major burns every two years or so. Many savanna and dry-forest plant species are called pyrophytes, meaning they are adapted in various ways to withstand occasional burning. Frequent fire is a factor to which rain forest species seem unable to adapt, although ancient charcoal remains from Amazon forest soils dating prior to the arrival of humans suggest that moist forests also occasionally burn. Experiments suggest that if fire did not occur in savannas in the Americas, species composition would change significantly. When burning occurs, it prevents competition among plant species from progressing to the point where some species exclude others, reducing the overall diversity of the ecosystem. But in experimental areas protected from fire, a few perennial grass species eventually come to dominate, outcompeting all others. 【】Evidence from other studies suggests that exclusion of fire results in markedly decreased plant-species richness, often with an increase in tree density. 【】There is generally little doubt that fire is a significant factor in maintaining savanna, certainly in most regions.8.【】On certain sites, particularly in South America, savanna formation seems related to frequent cutting and burning of moist forests for pastureland. 【】Increase in pastureland and subsequent overgrazing have resulted in an expansionof savanna. The thin upper layer of humus (decayed organic matter) is destroyed by cutting and burning. Humus is necessary for rapid decomposition of leaves by bacteria and fungi and for recycling by surface roots. Once the humus layer disappears, nutrients cannot be recycled and leach from the soil, converting soil from fertile to infertile and making it suitable only for savanna vegetation. Forests on white, sandy soil are most susceptible to permanent alteration.14.Prose SummarySeveral factors seem to play important roles in savanna formation.Answer ChoicesA.Savannas can form in areas with a five- to eight-month wet season, but they morecommonly have a longer wet season.B.Soil stress caused by drought, extreme moisture, or low nutrient levels favors theformation of savannas.C.Studies conducted in various regions indicate that an upper layer of white, sandy,soil is present in most permanent savannas.D.Drought stress affects trees and shrubs in savannas far less than it affectssavanna grasses.E. Frequent fires is a major factor contributing to the formation andmaintenance of savannas.F. In some areas, human cutting and burning is associated with savannaformation, and increase in pastureland has led to savanna expansion.参考答案：1.C2.B3.D4.B5.A6.C7.A8.D9.B10.D11.C12.A13.C14.BEF。
托福阅读中的一句长难句讲解
托福阅读中的一句长难句讲解This nascent world system developed as a result of insatiable demands for nonlocal raw materials in different ecological regions where societies were developing along very similar evolutionary tracks toward greater complexity.本句话是来自tpo63：The Sumerians and Regional Interdependence 苏美尔人与区域相互依存这一句的难点在于：词汇难，术语多，结构复杂. 上下文逻辑理困难.第一步：句子成分划分和翻译同学们可以自己先划分句子成分，再看老师的划分。
This nascent world system + developed[ as a result of insatiable demands for nonlocal raw materials/ in different ecological regions]（where societies + were developing /along very similar evolutionary tracks/ toward greater complexity. )这句话主要有2部分：（一）主干句：主语：This nascent world system 谓语：developed 状语：as a result of insatiable demands for nonlocal raw materials in different ecological regions.这是一个有3个介词短语组成的状语结构：① as a result of insatiable demands由于贪得无厌的需求② (demands) for nonlocal raw materials对非本地的原材料的需求③ in different ecological regions（原材料）来自不同的生态区域⭐️难点2：这一些较难的生词/术语：1️⃣ nascent：“初生的、萌芽的”。
史上最全托福TPO1-31阅读 题材结构科目分类
史上最全托福TPO1-31阅读题材结构科目分类自然科学一、地质学冰川类1 OG：Green Icebergs2 TPO 15：Glacier Formation3 TPO 19：Discovering The Ice Ages地质现象1 OG：Geology and Landscape2 TPO 01：Groundwater3 TPO 02：Desert Formation4 TPO 03：Depletion of The Ogallala Aquifer5 TPO 07：The Geologic History of The Mediterranean6 TPO 12：Water in The Desert7 TPO 20：Fossil Preservation8 TPO 21：Geothermal Energy9 TPO 24：Lake Water10 TPO 28-1：Groundwater11 TPO 27-2：The Formation of Volcanic Islands二、天文学火星类1 TPO 08：Running Water On Mars2 TPO 25：The Surface of Mars其他行星类1 TPO 16：Planets in Our Solar System2 TPO 22：The Allende Meteorite生物科学一、植物学1 Sample：Opportunity and Competitors2 TPO 01：Timberline Vegetation on Mountains3 TPO 05：Minerals and Plants4 TPO 09：The Arrival of Plant Life in Hawaii5 TPO 22：Spartina6 TPO 25：The Evolutionary Origin of Plants二、动物学动物特点1 OG：Swimming Machines2 OG：Feeding Habits of East African Herbivores3 TPO 04：Deer Population of The Puget Sound4 TPO 13：Biological Clock5 TPO 15：A Warm-blooded Turtle6 TPO 17-3：Symbiotic Relationship动物变化1 Sample：Meteorite Impact and Dinosaur Extinction2 TPO 05：The Cambrian Explosion3 TPO 08：Extinction of The Dinosaurs4 TPO 15：Mass Extinctions5 TPO 31-1: Speciation in Geographically Isolated Populations6 TPO 30-2： The Pace of Evolutionary Change动物行为1 TPO 02：The Origins of Cetaceans2 TPO 11：Begging by Nestlings3 TPO 11：Orientation and Navigation4 TPO 17：Ani mal Signals in The Rain Forest5 TPO 30-1 Role of Play in Development6 TPO 29-2：Competition7 TPO 28-3：Buck Rubs and Buck Scrapes8 TPO 27-3：Predator-Prey Cycles三、生态/环境/能源1 TPO 03：The Long-Term Stability of Ecosystems2 TPO 19：Succession, Climax, and Ecosystems3 TPO 26：Survival of Plants and Animals in Desert Conditions4 TPO 31-3: Savanna Formation1 Sample：Electricity from Wind2 TPO 04：Petroleum Resources3 TPO 29-3：The History of Waterpower3 TPO 10：Variations in The Climate4 TPO 18：Lightning5 TPO 23：Urban Climates社会科学一、艺术绘画/雕塑/陶瓷1 Sample：Lascaux Cave Paintings2 TPO 04：Cave Art in Europe3 TPO 10：Chinese Pottery4 TPO 11：Ancient Egyptian Sculpture5 TPO 23：Rock Art of the Australian Aborigines6 TPO 29-1：Characteristics of Roman Pottery7 TPO27-1：Crafts in the Ancient near East建筑/戏剧/电影/摄影1 OG：Applied Arts and Fine Arts2 TPO 01：The Origins of Theater3 TPO 02：Early Cinema4 TPO 03：Architecture5 TPO 12：Transition to Sound in Film10 TPO 22：The Birth of Photography二、历史/考古学工业化介绍1 OG：Artisans and Industrialization2 TPO 06：Powering The Industrial Revolution3 TPO 18：Industrialization in The Netherlands and Scandinavia4 TPO 26：Energy and the Industrial Revolution5 TPO 30-3: The Invention of the Mechanical Clock贸易/经济介绍1 TPO 10：Seventeenth-Century European Economic Growth2 TPO14：Pastoralism in Ancient Inner Eurasia3 TPO 16：Trade and The Ancient Middle East4 TPO 17：Europe’s Early Sea Trade with Asia5 TPO 25：The Decline of Venetian Shipping农业发展介绍 1 TPO 07：Agriculture, Iron, and The Bantu Peoples2 TPO21：The Origins of Agriculture3 TPO 23：Seventeenth-Century Dutch Agriculture国家/城市特点1 OG：Nineteenth-Century Politics in The United States2 TPO 07-2：Ancient Rome and Greece3 TPO 08：The Rise of Teotihuacan4 TPO 14：Maya Water Problems5 TPO 19：The Roman Army’s Impact on Britain6 TPO 26：Sumer and The First Cities of The Ancient Near East 人口变化特点1 TPO 05：The Origins of The Pacific Island People2 TPO 09：Colonizing The Americas Via The Northwest Coast3 TPO 20：Westward Migration4 TPO 20：Early Settlement in The Southwest Asia5 TPO 24：Moving into Pueblos6 TPO 28-2: Early Saharan Pastoralists三、心理/生理学1 OG：Aggression2 OG：The Expression of Emotion3 TPO06：Infantile Amnesia4 TPO 13：Methods of Studying Infant Perception5 TPO 18：The Mystery of Yawning6 TPO 21：Autobiographical Memory7 TPO 24：Breathing During Sleep四、社会学1 TPO09：Reflection in Teaching2 TPO 13：Types of Social Groups3 TPO 14：Childrenand Advertising4 TPO 31-2： Early Children Education其他学科类1 OG：Loie Fuller2 TPO 06：William Smith3 TPO 16：Development of The Periodic Table4 TPO 12：Which Hand Did They Use?结构体裁难度系数现象到解释：形成过程Exposition 现象到解释：形成过程Exposition现象到解释：形成过程：对比Exposition现象到解释Exposition现象到解释：原因：分类Exposition现象到解释Exposition现象到解释：形成过程Historical现象到解释：分类Exposition现象到解释Exposition现象到解释Exposition5现象到解释：对比Exposition 现象到解释：对比Exposition现象到解释Exposition现象到解释：总分Historical现象到解释Exposition现象到解释Exposition现象描述：分类Exposition现象到解释：分类Exposition现象到解释（含研究）理论解释（新旧对比）现象到解释（含研究）Exposition现象描述：分类Exposition现象到解释（含研究）Exposition现象到解释（含研究）Exposition现象到解释（含研究）Exposition现象到解释（含研究）Exposition现象到解释Exposition现象到解释总分：分类起源及发展Historical起源及发展Historical现象到解释：形成过程Exposition现象到解释总分：分类Historical HistoricalHistoricalHistoricalHistorical 现象到解释Historical 现象到解释Historical现象描述：分类Exposition起源及发展Historicalcandinavia起源及发展Historical现象到解释：总分Historical现象到解释：总分HistoricalHistorical 现象到解释：总分：Classificatio现象到解释： Classification Historical 现象到解释：总分Historical Exposition 现象到解释：总分：Classificatio现象到解释（含研究）Exposition 现象到解释（含研究）。
托福阅读句子插入题解题技巧
托福阅读中句子插入题的解题技巧在托福阅读考试中，同学们会遇到句子插入题。
那么本文就来探讨一下句子插入题的解题技巧供大家参考。
在做题的时候，我们需要先读句子插入题中出现的句子，再看原文。
这样做的好处是比较省时间，可以较快的找到被插入句子的主语。
而且重点把握该句的动词和名词，从而为读原文做好准备。
举个例子，比如TPO34中Passage 3 Protection of Plants by Insects里的第13题：Look at the four squares [] that indicate where the following sentence could be added to the passage.Sometimes they capture the insects to feed their protein-hungry larvae.Where does the sentence best fit?通过这句话，我们可以发现they是该句的主语，动词capture是谓语，而insects 是句子中的宾语，那么抓住这个句子的主干再去做题，就明确了回原文阅读的目的了。
下面我们来看原文：Ants are probably the most frequent and certainly the most persistent defenders of plants.[A] Since the highly active worker ants require a great deal of energy, plants exploit this need by providing extrafloral nectar that supplies ants with abundant energy.[B]To return this favor, ants guard the nectaries, driving away or killing intruding insects that might compete with ants for nectar.[C]Many of these intruders are herbivorous and would eat the leaves of the plants.[D]此时我们需要注意的，将句子插入原文后，插入后的句子不能改变原文间的内在逻辑关系。
托福阅读例题分析及答案
托福阅读例题分析及答案The answer to the question "What types of long-term stability do ecosystems achieve?" may be found in the passage's consideration of the assembly rules that underlie the structure of plant communities. Plant communities are able to achieve long-term stability assemblages through a combination of structuring factors that create both environmental filtering and species sorting. Environmental filtering results from the spatial heterogeneity found within plant communities, which creates micro-environments that select for certain traits. For example, some shaded areas may be more moist, while others may be drier. Species sorting results from the plant species' abilities to disperse and occupy different niches within the plant community. This process results in species becoming spatially separated, which reduces competition and increases stability.The assembly rules that underlie the structure of plant communities are key to understanding long-term stability in ecosystems. The assembly rules dictate which species can occupy certain niches, and in turn influence the species richness and diversity of theplant community. A plant community's species richness and diversity directly impact its ability to withstand environmental change. Plant communities with high species richness and diversity are more likely to have keystone species, which are essential to the health and function of the ecosystem. Keystone species play a particularly important role in maintaining ecosystem stability.A plant community's long-term stability also depends on its resiliency, or its ability to bounce back from environmental change or disturbance. Resilient plant communities are more likely to withstand perturbations, such as herbivore outbreaks or severe weather events, and are better able to recover once the disturbance has passed. Key factors influencing plant community resiliency include species richness and diversity, community evenness, and functional group diversity. Plant communities with high species richness and diversity are more likely to have keystone species, which are essential to the health and function of the ecosystem.The answer to the question "What are some factors that influence plant community assembly?" may be found in the passage's discussion of extrfloral nectaries.Extrfloral nectaries are structures located at the base of each sepal that attract several different species of ants. These ants provide protection to the plant by defending it from herbivores and competing plant species. In return for this protection, the plant provides the ants with nectar, which the ants collect and store in their underground chambers. These chambers serve as a source of water and food for the ants, as well as a refuge in case of emergency.The extrfloral nectary example is used to demonstrate how plants can attract specific pollinators or herbivore controllers to increase the health and function of the ecosystem. This is turn助于increase plant community assembly and long-term stability.答案示例：生态系统可以达到哪些类型的长期稳定性？答：生态系统可以达到的环境过滤和物种分类的长期稳定性。
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【实例解析】托福阅读句子插入题-Savanna Formation
句子插入题(InsertText
Questions)是托福阅读部分的必考题型，每篇文章后都会有一个该题型；且出题位置固定，为倒数第二道题。
该题型要求考生将一句话插入到原文四个黑色空格的其中一个当中，使得段落看起来更通顺。
那么，在以下内容中我们就为大家带来一些托福句子插入题的实例详解，希望能为大家的备考带来帮助。
托福阅读句子插入题：Savanna Formation
【Paragraph 5】Most savannas probably experience mild fires frequently and
major burns every two years or so. Many savanna and dry-forest plant species are
called pyrophytes, meaning they are adapted in various ways to withstand
occasional burning. Frequent fire is a factor to which rain forest species seem
unable to adapt, although ancient charcoal remains from Amazon forest soils
dating prior to the arrival of humans suggest that moist forests also
occasionally burn. Experiments suggest that if fire did not occur in savannas in
the Americas, species composition would change significantly. When burning
occurs, it prevents competition among plant species from progressing to the
point where some species exclude others, reducing the overall diversity of
the ecosystem. But in experimental areas protected from fire, a few perennial
grass species eventually come to dominate, outcompeting all others. ■Evidence
from other studies suggests that exclusion of fire results inmarkedly decreased plant-species richness, often with an increase i n tree density. ■There is generally little doubt that fire is a significant factor in maintaining savanna, certainly in most regions.
【Paragraph 6】■On certain sites, particularly in South America, savanna formation seems related to frequent cutting and burning of moist forests for pastureland. ■Increase in pastureland and subsequent overgrazing have resulted in an expansion of savanna. The thin upper layer of humans (decayed organic matter) is destroyed by cutting and burning. Humus is necessary for rapid decomposition of leaves by bacteria and fungi and for recycling by surface roots. Once the humus layer disappears, nutrients cannot be recycled and leach from the soil, converting soil from fertile to infertile and making it suitable only for savanna vegetation. Forests on white, sandy soil are most susceptible to permanent alteration.(Savanna Formation)
Look at the four squares [■] that indicate where the following sentence could
be added to the passage.
In addition, humans have contributed to the conditions favoring the formation
of savannas.
Where would the sentence best fit? 托福阅读句子插入题答案：3。