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。

These days, publishers in Ramistan of glossy Western-style magazines rarely need to worry about interference from the government — the magazines’ content promotes consumption, and convincing Ramistan’s emerging middle class to spend their money is a key component of domestic policy. 想问选项A的and convincing是修饰谁的呢？修饰content的话为什么可以在前面加and？ 选项C为什么语法不正确呢？

plums are 75% water. prunes are 15% water. how much water must be evaporated for x kg of prunes? 这是我今天考场上的题，好像做错了。我乱选了（85x/15） 其他选项有各种 25x/85，15x/75什么的。应该怎么做？

一辆车，车轮上有一点离圆心 d cm，车子前进 D cm，问该点距离/车子前进的距离？ 1. d等于一个值 2. D等于一个值

Shoppers at Retailer R who purchased substitute items from other manufacturers on DayI paid a total amount that was approximately 78 of the total shoppers would have paid had each of them been able to purchase ProductXon Day 1. “was 和 would have paid ”都在一个从句里，怎末会有两个谓语动词？“had each of them been able to...”这部分是跟谁啊？看不懂

On his drive to work, Leo listens to one of three radio stations, A, B, or C. He first turns to A. If A is playing a song he likes, he listens to it; if not, he turns to B. If B is playing a song he likes, he listens to it; if not, he turns to C. If C is playing a song he likes, he listens to it; if not, he turns off the radio. For each station, the probability is 0.30 that at any given moment the station is playing a song Leo likes. On his drive to work, what is the probability that Leo will hear a song he likes? 这个题目的0.3为什末代指在A station 播放到了自己喜欢的？不太理解0.3到底指的是甚麽

提问叶老师，这个题我不太理解为什么appear要用单数？ D选项，what 指什么？from what 这个倒装正常语序应该怎么写？

等腰直角三角形的周长为：16+16√2 ；问斜边的长度 等腰直角三角形的非直角边一样长：那设为x 所以斜边就为（根据勾股定理）x√2 所以周长：x+x+√2 x=16+16√2 2x+√2 x=16+16√2 X=8√2 斜边就等于：16 问题：X=8√2 是怎么算出来的？

为什么算到这一步(3^2-2^2)(3^2+2^2)(3^4+2^4)就能直接算答案了（答案:5x13x97），难道有4次方的地方不继续化简吗？我怎么知道要把公式简化到哪一步？

老师好 我这道题的方法就是解二次方程，只有唯一正解才能证明是充分的。（我发现很多应用题都是这样）但是我发现解二次方程很浪费时间，考试的时候可能没那么充分的时间，怎么办呢？这道题还有更好的方法吗？谢谢老师