Day 7

英文重现

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.

——GMAT OG 2015, Reading Comprehension, Passage 6

解析

1.整个句子很长，我们可以分别对主句和从句进行分析，遇到其他的主从复合句亦是如此。

我们先来看“because”引导的原因状语从句：

从句的主语是“vertical pressure gradients”，后面的“within the blood vessels”为介宾短语作定语，修饰“vertical pressure gradients”，谓语是一个被动结构“are counteracted”，“by”后面的内容为状语，引出“counteracted”这个动作的发出者（即主动语态中的

主语），因此从句可以简化为“Because vertical pressure gradients are counteracted”。

再看主句部分：

主句是一个“主系表”的结构，主语是“the distribution of blood”，后面的“throughout the body of sea snakes”为状语，系动词“remains”后面的“same”为表语，后面的

“regardless of…”为让步状语，最后的“provided they remain in the ocean”也是作状语，

所以，主句可简化为“the distribution of blood remains the same”。

那么整个句子的主干部分即为“Because vertical pressure gradients are counteracted，the distribution of blood remains the same”。

2.“regardless of”相当于“paying no attention to”，意为“不顾；不管”，后面可以

接名词或让步状语从句。例如：

The amount will be paid to everyone regardless of whether they have children or not.

不管有没有孩子，每个人都会得到相同的数额。

3.“provided（that）”相当于“providing (that)”和“on condition that”，表示“在……情况或条件下，只要……”。过去分词的一些结构可以在句中作状语，但不受句子的主语限制，也就是说，过去分词和主语不构成被动关系，如此处的“provided”与主语“the distribution of blood”，二者之间并没有被动的关系。再如下面这个句子：I will go, provided that you go too. 你也去的话我就去。其中“I”和“provided”之间也不是被动的关系。

词义辨析

参考翻译

因为血管内的垂直压力梯度被周围水中类似的压力梯度抵消掉了，所以水蛇体内的血液分布保持不变，不管它们（水蛇）在空间的方向如何，只要它们待在海里。

实战演练

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.

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.

答案：B

答案解析

根据“distribution of blood in the sea snake changes little while the creature remains in the

ocean”的意思可定位到文中的“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”，题目中“changes little”和句子中的“remains about the same”意思是一样的，题目问的是原因，所以我们应该重点看懂原文“because”从句的内容，即两种“pressure gradients”（vertical pressure gradients和similar pressure gradients）相互抵消（counteract），选项中提到“pressure”的只有选项B“水蛇周围的水压力梯度抵消了血管内的垂直压力梯度”和选项E“水蛇周围的水压力梯度的力量超过了水蛇循环系统内的垂直压力梯度的力量”，但是选项E中说的是一种压力“exceed”（超过）另一种压力，而非抵消，所以不正确，因此答案选B。

其他几个选项的意思分别为：

A.水蛇的心脏往往位于其身体的中心。

C.水蛇比陆生蛇类和树栖蛇类更少采用垂直姿势。

D.水蛇通常依靠肌肉收缩的波动将血液从躯干运输到头部。