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。

老师，麻烦讲解一下。

老师，这个题的思路里，p(r)那个式子不应该是等于 —1/24吗

老师，麻烦讲解一下。

老师，麻烦讲解一下。

It is an oversimplified view of cattle raising to say that ( all one has to do with cattle is leave them alone while they feed themselves, corral them, and to ) drive them to market when the time is ripe. (A) all one has to do with cattle is leave them alone while they feed themselves, corral them, and to (B) all one has to do with cattle is to leave them alone to feed themselves, to corral them, and (C) all one has to do with cattle is leave them alone while they feed themselves and then corral them and (D) the only thing that has to be done with cattle is leave them alone while they feed themselves, corral them, and (E) the only thing that has to be done with cattle is to leave them alone while they feed themselves, to corral them, and 答案是C，看到原文all one的时候很困惑，不知道指什么，再看到后面的they feed themselves直接就把A排除了，感觉指代有问题，然后竖着扫了一下，发现ACDE都是这种表达，而且B乍一看太平行了，尽管句末少了一个to，当时的想法是 就算有to也不敢选，因为不确定to leave them alone to feed themselves是否改变了句意，所以就不知道该选什么了。麻烦老师讲解。

Although it was expected that workers under forty would show hostility to the plan, the research report indicates that both ( younger and the older people ) approve of governmental appropriations for Social Security. (A) younger and the older people (B) younger people and the older (C) the younger and the older (D) younger and older people (E) people who are younger and those who are older 答案是D，错选了C。the加形容词不是可以表示一类人吗？而且感觉C在句意表达清楚的前提下看起来也比较工整。C和D的区别在哪？麻烦老师讲解。

A majority of the international journalists surveyed view nuclear power stations as unsafe at present but ( that they will , or could, ) be made sufficiently safe in the future. A. that they will, or could, B. that they would, or could, C. they will be or could D. think that they will be or could E. think the power station would or could 答案是D，错选了E。我对D的理解是这帮人认为现在核发电站是不安全的，但是认为将来他们可能是安全的。排除D是感觉they的指代有问题，不确实是在说这帮人还是核发电站。麻烦老师讲解。

In metalwork one advantage of adhesive-bonding over spot-welding is that the contact, and hence the bonding, is effected continuously over a broad surface ( instead of ) a series of regularly spaced points with no bonding in between. A. instead of B. as opposed to C. in contrast with D. rather than at E. as against being at 答案是D，这五个选项都不同，无法根据差异对比，而且对句意的把握也不太清晰，不知道该如何下手。麻烦老师讲解。

For some birds the sense of smell appears to paly a role in navigation, since pigeons with surgically removed olfactory nerves ( were found to have increased difficulties ) in homing. A. were found to have increased difficulties B. have been found to have increased difficulty C. were found to have increasing difficulty D. had been found to have increased difficulties E. have been found to have increasing difficulties 答案是B，我选的A。不明白为什么要用现在完成时，而且感觉困难应该是复数。麻烦老师讲解。

Those with a cynical turn of mind might ( speculate if the new corporation, eager for profit, might not have started ) the rumor that caused its competitor to declare bankruptcy. (A) speculate if the new corporation, eager for profit, might not have started (B) speculate if the new corporation, eager for profit, had not started (C) speculate if, in its eagerness for profit, the new corporation started (D) wonder as to whether, in its eagerness for profit, the new corporation did not start (E) wonder whether the new corporation, eager for profit, had started 答案是E，错选了B。做题时完全没有读明白句子意思，把speculate当成了spectacular，而且把if翻成了如果，怎么看怎么不顺，麻烦老师讲解。