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。

请问这题中“explore”的动发者为什么是“Lina”呢？我在读A选项时总觉得选项中explore的动发者是“A group of films” 因为觉得explore前面的主体是“A group of films”, 而 in 1970 和 Lina 都是修饰films的。

@英吉 请问这题E选项错在哪里呢？能麻烦您解释一下吗？谢谢！

老师您好，实在是有点看不懂这道题的问题到底要我算什么，求解，谢谢！

王文静老师，我是刚刚在上海结束了封闭班的学生，周梦瑶，^_^^_^不知道您还记不记得我，我准备在9.1日参加考试，我做了一个大致的复习计划，但是还不清楚，是否正确，或者有没有什么疏漏的地方，还想请您帮忙看一下，帮我修改斧正一下，非常感谢老师^_^^_^^_^

老师您好，我看了您明星课上给的题目答案过程，但是还是不太清楚自己的过程哪里出错了。能麻烦您解释一下吗？谢谢！ （我用紫色笔框出了我的解题过程）

请问老师，原文题目当中【即A选项】中estimates后面的and为什么前面没有逗号呢？这样没有逗号不就是跟从句后面surpassed并列了吗？可本应该是跟主句谓语并列呀？

请问一下老师此题中的选项B中的’ which were’的which不应该是要遵照定语从句中就近原则，来指代Richard Nixon吗？【我清楚人应该用whom来指代】可是为什么这里没有遵照就近原则呢？

老师您好，我听了您的基础课解释的为什么分子只能有一个C[1,60]，但是还是不太理解。在第一个班（e.g. senior）sibling里选一个是C[1,60]，另一个班就是C[1,1] 而不是C[1,60]呢？ 我不懂的点在于 题目说是两次选取都是random的，也就是在图中大写A里选出姐姐，不代表一定会在小写a 里选中她对应的妹妹呀？ 这里我比较糊，能麻烦老师您解释一下吗？谢谢！

老师，数学基础课这题 在可重复使用letter时，为什么在two letter code时不用✖️A[2,2]，在three letter code时 不用✖️A[3,3]呢？ 我是知道 当需要“选，拿，取”时，我们要用C，；但是我对具体什么时候需要用到A 还是有些模糊。能不能麻烦老师您解释一下我们什么时候会用到A？特别是在我们已经用到C后，什么时候需要在C基础上 再✖️A（e.g. C[3,26]✖️A[3,3]）？ 谢谢！

老师，能麻烦您解释一下您在数学基础课上说的 “因为k+7 可以整除3，所以整个式子可整除3” 的原因是什么吗？这里为什么可以直接判断出 k（k+7）可以被2整除呢？谢谢！