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。

为什么critique和envisioning不算并列？划线部分做同位语作用，为何不能用起伴随作用的DE？as well as是否既可以用在两者比较又可以用在三者？

请数学老师解答

请问数学老师 条件中 each more than 3 feet from the nearest wall 这个条件有什么用？再说下思路 谢谢老师

请问数学老师 条件2怎么可以快速推算结果

老师 我不太懂什么k一定是4的倍数呢？

ken老师这道题目答案对吗？为什么说两个条件中的方程是同一个方程啊，我算出来不一样，当条件1&2同时存在时，两个方程是有两个交点，应该就是可以判断出（a,b)的值吧？

请问数学老师 这个题如何在短时间内快速得出答案

ken老师 这道题目黄色部分我不太明白，An和n各自代表什么意思？我以为An代表的整数列所有数的合，那n不可能小于100呀，好奇怪

麻烦金老师回答，主要的困惑在于AB两个选项。一个that位置的不同，和will 和 would 的不同。刚开始我的思路是旅客会更多的使用旅行机构这件事是一个预测，没发生的，虚拟语气所以就错选了B.will 和would 的区别是 will 表达的感觉更确定一点吗？

麻烦金老师回答，这题看到DIGGING 这个动作是人发出的 不可能是化石发出的，排除AB ，C 里面的it 指代不是很清楚。对比DE， 这个化石来自那里这个部分的内容比较长所以D 选项是用了一个从句来说明的意思吗？就是关于DE选项的appears 和 APPEAR 这个差一点我不是很清晰，还是说D这个答案的what 这个选项引导的从句直接修饰到bones上，所以胜出？