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。

因为X和Y都是正整数，则只会发生两种情况，（X，Y）——（5，2）和（8，1）所以条件一说了X<8 则只会出现（5，2）的唯一情况，成立！条件二说Y>1 则也只能确定（5，2）的唯一情况，也成立呀！我选的D，就是一直找不出我的思维漏洞在哪，求解！

老师，听了OG精讲课程，老师是按照每个truck里面装三个shipments来解答的，但在这道题中并没有说到每个truck里装三个shipment，所以我觉得两个条件分别都不能，但合起来可以解答题目问题。请问我的思路有什么问题吗？

这题考点是so as to吗，为何这题E选项不能理解为to convert和for establishing平行呢

请问培月老师，看到选项我直接把DE排除了，因为airline被期望增加。。。这个语义很奇怪，应该是希望航空公司主动希望通过购买飞机来增加增加呀。所以在ABC里选了一个相对好的，请问这里的语义逻辑怎么考虑啊？

老师 428题我能选出来B（根据原文has led to...)但是在当时做题时我同时在纠结E选项。因为我不确定文中是在说说服还是在说需求。麻烦请郭培月老师解答一下～

我知道A和B错了，但是有个疑惑，““逗号”+非谓语”，所以A和B这里的prevented难道不是修饰主句的主语sound吗？为什么在这里用于修饰distances了呢。是老师说错了，还是我记错了？

C和E的排除中，老师给出的排除方法是在没有硬伤的情况下，主动优于被动，所以选择C选项。但是我当时的思路是，C当中的stationary在that的从句当中，只修饰到了troughts，而E当中的stationary则同时修饰crests和 troughts，在不知道troughts 和 crests是什么意思的情况下，我认为同时修饰两个要比单独修饰troughts好。就像以前那道uncontrolled和that was controlled那道题。

CDE排除的过程中，我的思路是who怎么能够就近修饰law firms呢，所以就选择了D，我也确实看到yet了，但是我认为可以做副词可以放过。请问我的思路有什么问题吗？

请问老师，这题条件二也推不出啊！条件二还有可能a大于1，这时候就不能确定x大于0了，所以是否答案应该选E？

最后留了ADE 觉得now部分应该作为结果伴随，排除A，在DE中选，因为about离knowledge越近越好，选了E 我想问问老师，1.这种ADE最后只有结构上的不同时，是由于句意重心导致选A的吗，着重强调现在有conclusion而非过去的研究；2.DE之间的对比，E把over 20年放中间来使得about。。离knowledge近是比D更好的吗。