GMAT阅读模拟试题考前练习3

>>GMAT模拟题练习：GMAT阅读模拟试题考前练习3

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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.

3、It can be inferred from the passage that which of the following is true of species of terrestrial snakes that often need to assume a vertical posture?

A.They are more likely to be susceptible to circulatory failure in vertical postures than are sea snakes.

B.Their hearts are less likely to be located at the midpoint of their bodies than is the case with sea snakes.

C.They cannot counteract the pooling of blood in lower regions of their bodies as effectively as sea snakes can.

D.The blood pressure at their midpoint decreases significantly when they are tilted with their heads up.

E.They are unable to rely on muscle contractions to move venous blood from the lower torso to the head.

正确答案：B

GMAT阅读题目解析

EThey are unable to rely on muscle contractions to move venous blood from the lower torso to the head.

unable不正确

问题说的是：经常保持(Assume)竖直状态的陆地蛇一下哪项推测正确。 定位词“assume a virticle poseture”

定位句讲的是海蛇心在中间，树蛇因为要在树上并且也保持直立所以脑袋离心脏超近。

即 直立=心脏近脑 海蛇=心脏中间

首先这是一个推断题，考察一步推理

定位“ 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. ”

选项分析：

A 陆地蛇容易circulatory failure ,与原文正好相反

B 和海蛇相比陆地蛇心脏不经常在身体中间 符合定位句一步推理

C 这个选项定位在开头，首先从定位位置就知道不像争确选项，再加上counteract the pooling of blood 正是陆地蛇的强项(adaptation)，因此错误

D 中间pressure 下降，定位文中发现这句话说的是海蛇，错误

E 错误，树蛇就是靠muscule 来输血

——by Elijah

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