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.

如果n是19的话n+1才是20。那a20不是应该等于a19+19吗，为什么会加20呢？条件二给的公式不是说a(n+1)=a(n)+n吗？我算的是1+2+...+19+19这样

@陆旭老师 第39题要怎么做呢？

@唐小梅老师 这道题用您的方法咋做呀？

@英吉老师 第715题的b选项为啥不算说了原文解释的对立面。是不是因为它主要讲的是electricity不是fossil fuel？ e选项这个地方算是要知道的常识吗？因为当时排除掉e选项就是因为自己脑袋里根本没有这个概念，感觉与原文无关。但是一旦听你说了，接受了说这个设定我是能理解的。所以以后再碰到这种不确定的情况，就默认判定这个选项是可行的，然后再去结合文章看是否支持原文逻辑链吗？

@陆旭老师 当出现overlapping info时，应该用matrix比较好还是用韦恩图比较好？

@英吉老师 如果这道题选了a，算是犯了什么错误？

请问老师这道题是不是答案给错了？不应该是4+8+12+...+200求和吗

想问一下小梅老师这道题的思路

想问一下小梅老师这道题如何快速得出答案？感觉自己解题思路有问题 2分钟内无法解答 类似题有没有什么快速切入的技巧？

A为什么不行？