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.

DS：如果x和y是≥0的数，问3^xy次方是多少？ 条件1：5^x=11^y 条件2：3^x=9^y 请问这题答案是B吗？谢谢老师！

不明白这道题的总体积为什么是（x+2）(y+2)(z+2)而不是（x+1）(y+1)(z+1);厚度不是1吗？谢谢！

我觉得这题答案应该是A吧？∵105拆分质因数可得105=3*5*7（3个完全不同的质因数）∴x+y+z=15。怎么会是C呢？？？？

向May提问，我觉得这题情况会分得很复杂，想听下老师的思路？

想向May老师提问。这题我知道条件1单独成立，但对条件2没什么思路，只能想到穷举法，当p等于2*5,3*5,3*5,2*3,2*5,3*5时，m等于2*3,2*3,2*5,5,3,2，然后一个个除发现有的余数是1，有的余数大于1，条件2单独不成立。想问老师这个思路对吗？有没有更加简洁的思路？

不懂此题。已知有A,B,C和D共4个人；问：现在从这四个人中选出3人，是ACD的概率是多少？请详细解释，谢谢老师！

不理解第一个条件均值如何得出关于6倍数的结论，是连续7个数除7余数为5则为6的倍数，所以有一个6的倍数？

不理解第一个条件均值如何得出关于6倍数的结论，是连续7个数除7余数为5则为6的倍数，所以有一个6的倍数？

第8题的思路是以BC为底，从F向BC做垂线，跟BC交点H，FH为三角形FBC的高。然后三角形BFH跟三角形BDC相似，h：30=BF：BD，但是BF长度未知，望老师解答。

第8题的思路是以BC为底，从F向BC做垂线，跟BC交点H，FH为三角形FBC的高。然后三角形BFH跟三角形BDC相似，h：30=BF：BD，但是BF长度未知，望老师解答。