我选了A，题目读懂了。但是听了好几个老师的录音，扯来扯去的还是没搞明白A为什么不对。请老师对A和D再做一个翻译和解释。以及这m种类型的题，应该从何入手。谢谢老师

assumptions题将答案锁定在带有否定的选项A和D，之后无法根据A和D的逻辑意思得出答案，请问如何解答。

题目问“assumptions”，由此排除主句没有否定的，留下了A和D，拿下一步该如何辨别呢？

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 he 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. 7. The primary purpose of the third paragraph is to 　　(A) Introduce a topic that is not discussed earlier in the passage 　　(B) Describe a more efficient method of achieving an effect discussed in the previous paragraph 　　(C) Draw a conclusion based on information elaborated in the previous paragraph 　　(D) Discuss two specific examples of phenomena mentioned at the end of the previous paragraph 　　(E) Introduce evidence that undermines a view reported earlier in the passage

老师，我只要碰到拿两事对比的逻辑题，总是分不清楚，老师，您能提下建议吗？谢谢

cr

之前老管说要提高对范围的敏感度的，范围是什么自己回去悟，可是悟了很久都不明白。求老鹰解释。

觉得ACDE都讲的是pretax price的变化， 原文只讲了税的变化，销售的下降和销售下降是因为税后价格，没讲到 pretax price, B 讲的是销售下降和tax变化的关系，沾边，所以选了。 听了以前录音的意思好像是说B的smaller tax increase 是相对比那1%的销售下降而说的，所以这样还否定了税是导致销售下降的因素，但是我读题时觉得smaller tax increase是相对eight-cent increase in tax说的，跟原文逻辑结构一致。 老师 这个思路有什么问题? 这个题光看沾边幅度大小选不出正确答案，考试中要怎么办

A C E都能很快的排除，B感觉原文提过，但是原文的主旨应该是销售额和价格之间的关系吧，那D比B好啊，这两个选项应该怎么比呢