GRE阅读3种常见主体结构精讲
GRE阅读看懂文章先了解结构 ,3种常见主体结构精讲，下面我就和大家共享，来观赏一下吧。
GRE阅读3种常见主体结构精讲
新GRE阅读理解文章的常见“主体结构”有三种：
1.结论-解释型(也叫论点-解释型)
2.新老观点对比型
3.现象解释型(包含问题-解决方案型)
GRE阅读文章结构精讲：结论-解释型
这类文章在开头有一个推断句，一般是文章的结论，也是文章的主题。这个推断句的谓语部分通常包含系动词(is, remain, prove, turn out, appear等)或情态动词(can, may, should, must等)，而且含有表示态度的词汇(如形容词等)。例如：
Becau of its accuracy in outlining the Earths subsurface, the ismic-reflection method remains the most important tool in the arch for petroleum rerves. In field practice, a subsurface is mapped by arranging a ries of wave-train sources, such as small dynamite explosions, in a grid pattern…
文章首句指出：由于“地震反射法”(sr)在勾划地球的地下层面这方面的精确 性，该方法始终是探寻石油储备的最重要的工具。这是一个推断句，为结论。其中remains为系动词，而most important为态度词，表示对“地震反射法”持特别正面的评价。
后文应解释“地震反射法”的详细过程。 其次句话对解释进行总的说明：“在实地作业中，通过将一系列波列源，诸如小规模炸药爆炸，排列成一个网格模式，从而将地下层面标绘出来。”接下来是“地震反射法”的具体过程。
GRE阅读文章结构精讲：新老观点对比型
这类文章在开头提出老观点，然后提出新观点并进行论述。通常新观点是文章的主题。老观点消失的标志词有：
1.传统观点： has been, traditionally, until recently等。
2.大众观点：frequently, widely, many等。
新观点消失的标志词有：however, recently, now等。
例如：
Traditionally, pollination by wind has been viewed as a reproductive process marked by random events in which the vagaries of the wind are compensated for by the generation of vast quantities of pollen, so that the ultimate production of new eds is assured at the expen of producing much more pollen than is actually ud。
However, a number of features that are characteristic of wind-pollinated plants reduce pollen waste…
文章首句指出：“传统上，风媒授粉过程始终被视为是一个以随机大事为标志的繁殖过程，其中风的不确定性通过产生大量花粉而得以补偿，因此，新种子的最终繁殖得以保证，
而此举的代价是所需产生的花粉要远远超过实际的使用量。”由第一个词traditionally可知文章首句为老观点(由于风的不确定性，风媒植物要产生大量花粉补偿)，那么本文的结构是“新老观点对比型”。
其次段首句消失了GRE阅读中的标志性转折词however,说明这句话就是新观点：“但是，风媒植物所独有的一系列特征可削减花粉铺张。”这说明风媒植物除了可以产生大量花粉加以补偿的消极策略之外，还可以通过一些乐观机制削减花粉损失，不肯定需要产生大量花粉。
GRE阅读文章结构精讲：现象解释型
文章开头提出一个现象，然后解释现象。解释是主题。有多个解释时，一般对前面的解释持负面评价，对最终的解释持正面评价。提消失象时的标志词有：phenomenon, fact; problem, difficulty, puzzle, question等。例如：
What caus a helix in nature to appear with either a dextral (right-handed,or clockwi) twist or a sinistral (left-handed, or counterclockwi) twist is one of the most in
triguing puzzles in the science of form…What mechanisms, control handedness and keep left-handedness rare?
It would em unlikely that evolution should discriminate against sinistral snails if sinistral and dextral snails are exact mirror images, for any disadvantage that a sinistral twist in itlf could confer on its posssor is almost inconceivable. But left- and right-handed snails are not actually true mirror images of one another…
是什么样的缘由致使自然界中的螺旋体呈现出右旋(“右向旋转的”，或顺时针的)或左旋(“左向旋转的，”或反时针的)?这是形态科学中一个最引人入胜的不解之谜。毕竟是一些什么样的机制掌握着旋转方向，并使左旋的比例为数稀有呢?
但是，这种结合不对称、解剖学和偶然性的进化论机制并未供应一种充分的解释，以说明蜗牛的右旋何以会成为主要的旋向。于是，进化论必需让位于支持右旋或左旋的明确的发育机制为基础的理论。因此，解决全部蜗牛身上旋向之谜的道路好像与这一螺旋体本身一样曲折简单。
上文在第一段最终提出一个问题：“毕竟是一些什么样的机制掌握着旋转方向，并使左旋的比例为数稀有呢?”这个问题就是一个现象：螺旋体中左旋的比例少。有问题就有解答，有现象就有解释。其次段从进化论的角度解释这一现象。但是，GRE阅读文章中一般对进化论的解释持负面评价，所以需要查找新的解释。第三段否定了进化论的解释。在末段，以发育机制(developmental mechanism)解释“为何左旋少、右旋多”。
把握了文章的三种主体结构以后，做文章后的很多题时易如反掌。
本文的结构是“结论-解释型”，因此(C)为正确答案。由此可见，对于GRE阅读来说，把握文章的主体结构，而不陷入文章词句与细节的泥沼中，是一件快意的事情：文章读得爽，题也做得爽。
GRE阅读练习每日一篇
If a supernova (the explosion of a massive star) triggered star formation from den clouds of gas and dust, and if the most massive star to be formed from the cloud evolved into a supernova and triggered a new round of star formation, and so on, then a chain of
star-forming regions would result. If many such chains were created in a differentially rotating galaxy, the distribution of stars would remble the obrved distribution in a spiral galaxy (spiral galaxy: n.(=spiral nebula)螺旋星云,旋涡星云).
This line of reasoning underlies an exciting new theory of spiral-galaxy structure. A computer simulation bad on this theory has reproduced the appearance of many spiral galaxies without assuming an underlying density wave, the hallmark (a distinguishing characteristic, trait, or feature “the dramatic flourishes which are the hallmark of the trial lawyer Marion K. Sanders”) of the most widely accepted theory of the large-scale structure of spiral galaxies. That theory maintains that a density wave of spiral form sweeps through the central plane of a galaxy, compressing clouds of gas and dust, which collap into stars that form a spiral pattern.
17. The primary purpo of the passage is to
(A) describe what results when a supernova triggers the creation of chains of star-forming regions
