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。

如果n是19的话n+1才是20。那a20不是应该等于a19+19吗，为什么会加20呢？条件二给的公式不是说a(n+1)=a(n)+n吗？我算的是1+2+...+19+19这样

@陆旭老师 第39题要怎么做呢？

@唐小梅老师 这道题用您的方法咋做呀？

@英吉老师 第715题的b选项为啥不算说了原文解释的对立面。是不是因为它主要讲的是electricity不是fossil fuel？ e选项这个地方算是要知道的常识吗？因为当时排除掉e选项就是因为自己脑袋里根本没有这个概念，感觉与原文无关。但是一旦听你说了，接受了说这个设定我是能理解的。所以以后再碰到这种不确定的情况，就默认判定这个选项是可行的，然后再去结合文章看是否支持原文逻辑链吗？

@陆旭老师 当出现overlapping info时，应该用matrix比较好还是用韦恩图比较好？

@英吉老师 如果这道题选了a，算是犯了什么错误？

请问老师这道题是不是答案给错了？不应该是4+8+12+...+200求和吗

想问一下小梅老师这道题的思路

想问一下小梅老师这道题如何快速得出答案？感觉自己解题思路有问题 2分钟内无法解答 类似题有没有什么快速切入的技巧？

A为什么不行？