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.

【请May老师回答】这题鸡精提供的答案是D 可是我觉得第二个条件不能得出呢 假设n三次方是x平方 除以n平方 是可以得到x/ n 平方 但是x/n 不一定是整数呀？

7.15/寂静：STUVW, 5个人， V和W中间必须隔一个人，求问共有几种组合？ 我的想法是这样的A（3,3）*A(2,2)*C(3,1)=36种；思路如下：先把V+C(3,1)+W看成一个整体；可得：A(2,2)*C(3,1)种排法；然后5个人可分成三类，于是A(3,3)。不知道我的想法对不对，请老师解答。感激不尽！

急求此题！谢谢老师！题目来7/6自寂静。x∈{1, 2, 3}，y∈{4,5,6}，z∈{7,8,9}，求yxx与z的乘积为偶数的概率？我根据求反可得：2/3x1/3x2/3=4/27 1-4/27=23/27 不等于5/9呀？我就是卡在这里了求教。谢谢！

请郭老师看一下这几题 谢谢老师

麻烦郭老师看一下这几题，谢谢老师

麻烦郭老师看一下这几题，谢谢

请郭老师帮我看一下这几道题，好几个都完全不会…

请郭老师帮我看一下这几道题，好几个都完全不会…

不是很明白为什么A选项不对 我觉得outnumber了给其他人写信的数量可以作为这个period Emily写信的结果出现 为什么不能用现在分词呢？