Day 7

英文重現

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.整個句子很長，我們可以分別對主句和從句進行分析，遇到其他的主從復合句亦是如此。

我們先來看“because”引導的原因狀語從句：

從句的主語是“vertical pressure gradients”，后面的“within the blood vessels”為介賓短語作定語，修飾“vertical pressure gradients”，謂語是一個被動結構“are counteracted”，“by”后面的內容為狀語，引出“counteracted”這個動作的發出者（即主動語態中的

主語），因此從句可以簡化為“Because vertical pressure gradients are counteracted”。

再看主句部分：

主句是一個“主系表”的結構，主語是“the distribution of blood”，后面的“throughout the body of sea snakes”為狀語，系動詞“remains”后面的“same”為表語，后面的

“regardless of…”為讓步狀語，最后的“provided they remain in the ocean”也是作狀語，

所以，主句可簡化為“the distribution of blood remains the same”。

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

2.“regardless of”相當于“paying no attention to”，意為“不顧；不管”，后面可以

接名詞或讓步狀語從句。例如：

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

不管有沒有孩子，每個人都會得到相同的數額。

3.“provided（that）”相當于“providing (that)”和“on condition that”，表示“在……情況或條件下，只要……”。過去分詞的一些結構可以在句中作狀語，但不受句子的主語限制，也就是說，過去分詞和主語不構成被動關系，如此處的“provided”與主語“the distribution of blood”，二者之間并沒有被動的關系。再如下面這個句子：I will go, provided that you go too. 你也去的話我就去。其中“I”和“provided”之間也不是被動的關系。

詞義辨析

參考翻譯

因為血管內的垂直壓力梯度被周圍水中類似的壓力梯度抵消掉了，所以水蛇體內的血液分布保持不變，不管它們（水蛇）在空間的方向如何，只要它們待在海里。

實戰演練

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

根據“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”，題目中“changes little”和句子中的“remains about the same”意思是一樣的，題目問的是原因，所以我們應該重點看懂原文“because”從句的內容，即兩種“pressure gradients”（vertical pressure gradients和similar pressure gradients）相互抵消（counteract），選項中提到“pressure”的只有選項B“水蛇周圍的水壓力梯度抵消了血管內的垂直壓力梯度”和選項E“水蛇周圍的水壓力梯度的力量超過了水蛇循環系統內的垂直壓力梯度的力量”，但是選項E中說的是一種壓力“exceed”（超過）另一種壓力，而非抵消，所以不正確，因此答案選B。

其他幾個選項的意思分別為：

A.水蛇的心臟往往位于其身體的中心。

C.水蛇比陸生蛇類和樹棲蛇類更少采用垂直姿勢。

D.水蛇通常依靠肌肉收縮的波動將血液從軀干運輸到頭部。