这道题正确答案是 B， 我一直觉得是D, 不是特别明白 B 答案为什么 说as effectively as sea snakes can? 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. 20. 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 titled with their heads up.

老师，我今天考试碰到的寂静题，一模一样！然后根本算不出来啊，两个式子结合是30x=5y.不知道寂静答案是怎么算出来x=15 y=90的？

请May老师解答～ 老师，您回复我的这一题，关于圆心角 和 圆周角，我有几个问题想问： 1. ABC是一个优弧，优弧的圆心角是怎么看的呢？为什么是∠BOC，而不是∠AOC呢？ 2. 此图中，（优弧）弧ABC 和 （劣弧） 弧AC是否有同一个圆心角 和 同一个圆周角呢？ 如果不是，老师可否分别把此图中 优弧与劣弧的圆心角和圆周角画一下？ 2. 优弧ABC所对应的圆周角 是∠E（我用红笔加上去的那一个）吗？

请May老师解答，想问一下鸡精的答案是不是错了？我的解答过程有没有问题？

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