According to a theory advanced by researcher Paul Martin，the wave of species extinctions that occurred in North America about 11,000 years ago，at the end of the Pleistocene era，can be directly attributed to the arrival of humans，i.e.，the Paleoindians， who were ancestors of modern Native Americans. However，anthropologist Shepard Krech points out that large animal species vanished even in areas where there is no evidence to demonstrate that Paleoindians hunted them.Nor were extinctions confined to large animals： small animals，plants，and insects disappeared，presumably not all through human consumption. Krech also contradicts Martin's exclusion of climatic change as an explanation by asserting that widespread climatic change did indeed occur at the end of the Pleistocene. Still，Krech attributes secondary if not primary responsibility for the extinctions to the Paleoindians，arguing that humans have produced local extinctions elsewhere.But，according to historian Richard White，even the attribution of secondary responsibility may not be supported by the evidence. White observes that Martin's thesis depends on coinciding dates for the arrival of humans and the decline of large animal species，and Krech，though aware that the dates are controversial，does not challenge them；yet recent archaeological discoveries are providing evidence that the date of human arrival was much earlier than 11,000 years ago. 　3. In the last sentence of the passage， the author refers to “recent archaeological discoveries” (lines 27-30) most probably in order to 　　(A) Refute White's suggestion that neither Martin nor Krech adequately account for Paleoindians' contributions to the Pleistocene extinctions 　　(B) Cast doubt on the possibility that a more definitive theory regarding the causes of the Pleistocene extinctions may be forthcoming 　　(C) Suggest that Martin's， Krech's， and White's theories regarding the Pleistocene extinctions are all open to question 　　(D) Call attention to the most controversial aspect of all the current theories regarding the Pleistocene extinctions 　　(E) Provide support for White's questioning of both Martin's and Krech's positions regarding the role of Paleoindians in the Pleistocene extinctions 老师，我在做这道题的时候，首先定位到最后一句觉得没说什么重点，就有个yet转折，可能这是用来驳斥前面的某些观点的。所以看选项找有没有驳斥的意思的， 发现5个选项全都在驳斥。。。心里慌了往前找。再回去找的时候时间已到。我就随便选了个B（时间一到各种混乱），因为在做这篇文章之前，我大体看了下原文，记住了原文讲的是P反驳M，W反驳P。后来答案我也看明白了，我认为我做这道题的思路出现了偏差，我想问一下应该怎么修正。

这个是怎么算的，我只能看出要求的人数是总人数的百分之三

这题除了试数还有什么好方法吗？如果试数的话，如何快速找到适合的数呢？

条件二说的是每一项Sn都大于5吗？，但是n/（n+1）不是小于1吗？我不知道该怎么理解和使用该条件

条件2是要把对角线为8时的情况算出来吗？如果不是，应该怎么判断吗？另外五边形的面积应该怎么算呢？

这题怎么思考？还有绝对值不等式的考点有哪些啊

B单独不能成立吗？k=7带入不等式中，不是可以限制m和n的范围吗

题干不是已经能排出+和➗好了吗？因为此时式子没有意义。那两个条件为什么不能单独成立呢？这题的逻辑是什么

条件2为什么单独不成立？B做了超过50%，说明B比A效率高，那么3小时内可以完成

已知由一个符号@表示的加减乘除中的一一个符号。如果a@ (-a) =0,那么a=0.问:以下条件能否判断符号@是加减乘除中的哪一个?条件1).其中a@(a@a)=0, a=0;条件2).其中a@(b@c)=(a@b)@c. 答案：E

老师这道题和后面你讲的6和4的例子没看懂！