我们大家在备考gmat考试的时候对于阅读部分都是先要加强自己的词汇积累能力，这样的话在读文章的时候时间也快了，文章也能够读得懂了，那么下一步就是做题了，今天小编为大家带来的就是GMAT阅读经典实例讲解。
文章：
In terrestrial environments, gravity places special demands on the cardiovascular systems of animals. Gravitational pressure can cause blood to pool in the lower regions of the body, making it difficult to circulate blood to critical organs such as the brain. Terrestrial snakes, in particular, exhibit adaptations that aid in circulating blood against the force of gravity.
The problem confronting terrestrial snakes is best illustrated by what happens to sea snakes when removed from their supportive medium. Because the vertical pressure gradients within the blood vessels are counteracted by similar pressure gradients in the surrounding water, the distribution of blood throughout the body of sea snakes remains about the same regardless of their orientation in space, provided they remain in the ocean. When removed from the water and tilted at various angles with the head up, however, blood pressure at their midpoint drops significantly, and at brain level falls to zero. That many terrestrial snakes in similar spatial orientations do not experience this kind of circulatory failure suggests that certain adaptations enable them to regulate blood pressure more effectively in those orientations.
One such adaptation is the closer proximity of the terrestrial snake’s heart to its head, which helps to ensure circulation to the brain, regardless of the snake’s orientation in space. The heart of sea snakes can be located near the middle of the body, a position that minimizes the work entailed in circulating blood to both extremities. In arboreal snakes, however, which dwell in trees and often assume a vertical posture, the average distance from the heart to the head can be as little as 15 percent of overall body length. Such a location requires that blood circulated to the tail of the snake travel a greater distance back to the heart, a problem solved by another adaptation. When climbing, arboreal snakes often pause momentarily to wiggle their bodies, causing waves of muscle contraction that advance from the lower torso to the head. By compressing the veins and forcing blood forward, these contractions apparently improve the flow of venous blood returning to the heart.
1. The passage provides information in support of which of the following assertions?
A The disadvantages of an adaptation to a particular feature of an environment often outweigh the advantages of such an adaptation.
B An organism’s reaction to being placed in an environment to which it is not well adapted can sometimes illustrate the problems that have been solved by the adaptations of organisms indigenous to that environment.
C The effectiveness of an organism’s adaptation to a particular feature of its environment can only be evaluated by examining the effectiveness with which organisms of other species have adapted to a similar feature of a different environment.
D Organisms of the same species that inhabit strikingly different environments will often adapt in remarkably similar ways to the few features of those environments that are common.
E Different species of organisms living in the same environment will seldom adapt to features of that environment in the same way.
正确答案：
B
题目释义：
细节题目
考点：
应用(Application)
旨在考察我们对文章细节的深度认知，并达到可以应用总结的地步。
这个题目很难定位，即是要对于全文的细节做一个了解，然后选择。这道题的错误选项基本都是文章中没有提到的。
选项分析：
(A) 一个对特定环境特征的适应性的缺点远大于这个适应性的优点。文中没有提到过适应性的优缺点问题，这个选项属于无中生有。
(B) Correct。一个生物体在被放到一个不适应的环境时有时会说明那些被适应这个环境的适应性所解决的问题。这个选项可以定位在第二段中，水蛇被拿出水自然适应不了陆地的重力系统，但是与水蛇有相似特征的陆地蛇并没有死，这就说明了陆地蛇必然有适应性存在。并且这个适应性解决了这个重力的问题。与该选项的意思相符。
(C) 生物体对特定环境的独特特征的适应性的有效与否只能通过这个生物群体的其他物种适应的不同环境的同样特征的有效性来检验。在选择中，尽量避开文中没有明显提及的“极端”词汇。比如这个选项的“only”。另外，这个选项的内容在文中也没有明显涉及。
(D) 同种类的生物体居住在极为不同的环境中通常对这些环境的为数不多的相同点有着显著的相同的适应方法。文中没有提及这个选项的内容，无中生有。
(E) 不同物种的生命体在相同的环境下不会用同样的方法适应环境的特征。这个选项没有根据。文中也没有提及说不同物种的适应方法。
题目详解：
2. According to the passage, one reason that the distribution of blood in the sea snake changes little while the creature remains in the ocean is that
A the heart of the sea snake tends to be located near the center of its body
B pressure gradients in the water surrounding the sea snake counter the effects of vertical pressure gradients within its blood vessels
C the sea snake assumes a vertical posture less frequently than do the terrestrial and the arboreal snake
D the sea snake often relies on waves of muscle contractions to help move blood from the torso to the head
E the force of pressure gradients in the water surrounding the sea snake exceeds that of vertical pressure gradients within its circulatory system
正确答案：
B
题目详解：
题目释义：
细节题目
考点：
支持主题(Supporting ideas)
旨在考察我们对文章细节的认知
这个题目答案定位在第二段“Because the vertical pressure gradients within the blood vessels are counteracted by similar pressure gradients in the surrounding water, the distribution of blood throughout the body of sea snakes remains about the same regardless of their orientation in space, provided they remain in the ocean.”答案选项几乎是这句话的意译。
选项分析：
(A) 海蛇的心脏在其身体中部附近。这个选项的关键词出现在文章的第三段。但是这并非是海蛇血液分配均匀的原因，相反的，这是陆蛇适应性的一个表现。
(B) Correct. 重力与海洋的浮力相互抵消。这个考点中解释了，此处不做赘述了。
(C) 海蛇相比于陆蛇和树蛇，不经常摆竖直pose。这个选项的依据是第三段说树蛇经常摆竖直pose。不过同样，文中并没有说这点是海蛇血液分布均匀的原因，其实海蛇无论什么pose，都没事，因为浮力会抵消重力。
(D) 海蛇经常通过肌肉的收缩让来让血液从身体流入大脑。这个是树蛇的办法，不是海蛇的办法。
(E) 海洋的浮力比重力的力量要强。找回定位句，有“similar”一词，所以这个“exceeds”是错误的。
3. The author suggests that which of the following is a disadvantage that results from the location of snake’s heart in close proximity to its head?
A A decrease in the efficiency with which the snake regulates the flow of blood to the brain
B A decrease in the number of orientations in space that a snake can assume without loss of blood flow to the brain
C A decrease in blood pressure at the snake’s midpoint when it is tilted at various angles with its head up
D An increase in the tendency of blood to pool at the snake’s head when the snake is tilted at various angles with its head down
E An increase in the amount of effort required to distribute blood to and from the snake’s tail
正确答案：
E
题目详解：
题目释义：
细节题目
考点：
推断(Inference)
旨在考察我们对文章的深度理解，以及逻辑推断能力。
这个题目定位比较明显，在第3段中“Such a location requires that blood circulated to the tail of the snake travel a greater distance back to the heart, a problem solved by another adaptation. ”
选项分析：
(A) 蛇调整血流向脑的效率下降。文中没有提到过，而且从行文的发展来看，似乎这个选项说反了。因为离脑近了，血流向脑的速度和效率应该会上升。
(B) 蛇能朝向的不会影响血流的方向数减少。文中也没有提到这一点，提到“方向”这个词的是在第二段，但说的是水蛇不会因方向而影响血流。
(C) 当其昂起头时，蛇身体中部的血压下降。这个选项在文中找不到根据，比较容易排出。
(D) 当蛇低头时，增加了血涌向大脑的趋势。这个选项在文中找不到根据，比较容易排出。
(E) Correct。需要更大的努力以让血流流向蛇尾。因为原文介绍了，心到蛇尾的距离增大了，所以需要的“努力”也自然就多了。
4. In the passage, the author is primarily concerned with doing which of the following?
A Explaining adaptations that enable the terrestrial snake to cope with the effects of gravitational pressure on its circulatory system
B Comparing the circulatory system of the sea snake with that of the terrestrial snake
C Explaining why the circulatory system of the terrestrial snake is different from that of the sea snake
D Pointing out features of the terrestrial snake’s cardiovascular system that make it superior to that of the sea snake
E Explaining how the sea snake is able to neutralize the effects of gravitational pressure on its circulatory system
正确答案：
A
题目详解：
题目释义：
主旨题目
考点：
主旨(Main idea)
旨在考察我们对文章整体的把握程度，对文章的结构的分析能力和把控能力，以及对作者逻辑的判断。
其实这篇文章主要的目的是向读者介绍蛇对与重力系统的适应性。其中包括了水蛇怎么怎么样，来引出陆地上的蛇必然有的适应性。
选项分析：
(A) Correct。解释让陆生蛇能够配合重力系统影响的适应性。全文整体都一直在说蛇对于重力的适应性。
(B) 比较水蛇和陆蛇的循环系统。文章中确实提到了水蛇和陆蛇的循环系统。不过作者逻辑上的主要意思不在于此，是想利用这个说明蛇对重力系统的适应性。
(C) 解释为什么陆蛇和海蛇的循环系统不同。这个选项还是比较有迷惑性的。文中解释了为什么海蛇与陆蛇不同，原因就是适应性的一个表征。而行文中作者也确实说的是这个。不过这个选项把重点搞错了，作者的逻辑目的并不是解释为什么不同，而是要解释适应性，所以甚至可以把这个循环系统的不同当做一个说明适应性的载体。
(D) 指出陆蛇的心血管系统要强于海蛇的心血管系统。这个选项文中没有提到。即便陆蛇的心血管系统因适应性而比较适合陆生也没有证据能说明让陆蛇的心血管系统更强水蛇，而且也不是作者的主题。
(E) 解释海蛇如何抵消重力对循环系统的影响。这个选项文中提到了，是靠海水浮力(这不是海蛇的能力，be able to 在选项中给我们的理解是水蛇的某种自身能力抵消的重力)，而且这不是作者的中心意思。
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