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.

求may老师解答

求may老师解答

老师你好，数学课本第29页例4题，我没看懂解答1和2中的组合问题。谢谢！

这一题没看懂是怎么解M和N的，为什么等于84？不是改86吗？

老师没听懂，哪里来的2呢

2的三次方 5的三次方是什么呀？

np 2*2是什么意思 不懂为什么选E

老师你好 这道题的n怎么选数字来解它 那么多数字 为什么偏要选择0 1 2…？

老师你好，左边这道题解法听明白了，但是3k加2乘以15k加3这个方程不会解，最近看好多题都是不知道怎么解方程，我全忘了。数学书我看了，有概念，但是没教怎么解方程的！请先告诉我这道题那个地方是怎么回事，再教我怎么做，谢谢！