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。

有24个brand，对每个brand的四个方面进行评估，这四个方面是ABCD，评估结果有四种，excellent，good，not good，bad，至少有几个brand的两个方面either excellent or good？ （1）至少有10个brand的两个方面是excellent （2）至少有12个brand的三个方面是good

a/c是否小于1？ （1） a/（c-1）小于1 （2） （a-1）/c小于1

切线与圆

PS：总共66个学生，有18个是business major，24个是新生，还有36个什么也不是，我忘了最后是问，仅仅是新生不是business major 的还是仅仅是business major不是新生的？ 构筑答案：好像答案不是12 就是16.。。 解析： 18和24代表的韦恩图圈圈有重合，36代表的是自己单独的圈圈。 Total =66； 36个学生不在Business和Fresh 范畴里面，所以F+B=30; F 和B的共有学生=12， 是B不是F=6； 是F不是B=12。

PS：挺简单的，就是一个数轴吧-5到15都涂黑了，然后问哪个式子能代表？ |x-5|<10 这个不等式怎么解来着？忘了。。。变号问题

PS：讲一个租赁汽车的公司每一次购买会购买5辆新车，每次卖掉会卖掉3辆旧车，今年新增了14辆车，把每次买和每次卖都算做一次交易，问今年最少做了几次交易？

If it took Carol 1/2 hour to cycle from his house to the library yesterday, was the distance that he cycled greater then 6 miles? ( 1mile=5,280feet) (1) The average speed at which Carlos cycled from his house to the library yesterday was greater than 16 feet per second. (2) The average speed at which Carlos cycled from his house to the library yesterday was less than 18 feet per second

Of the 12 temporary employees in a certain company, 4 will be hired as permanent employees. If 5 of the 12 temporary employees are women, how many of the possible groups of 4 employees consist of 3 women and one man? A. 22 B. 35 C. 56 D. 70 E. 105

if x is positive, is x >3 1. (x-1)^2 >4 2. (x-2)^2 >9

if the average of the consecutive even integers a,b, and c is less than 13a, which of the following best describes the value of a? 答案： a is positive 为什么呢？