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。

请问老师这道鸡精题解题思路

我想问第49题，第二个条件，由公示得出f（a）*f（b）=10a方✖️10b方=100a方✖️b方，所以只能a方✖️b方为0，所以结果为0？

文章：According to many analysts, labor-management relations in the United States are undergoing a fundamental change: traditional adversarialism is giving way to a new cooperative relationship between the two sides and even to concessions from labor. These analysts say the twin shocks of nonunion competition in this country and low-cost, high-quality imports from abroad are forcing unions to look more favorably at a variety of management demands: the need for wage restraint and reduced benefits as well as the abolition of "rigid" work rules, seniority rights, and job classifications. Sophisticated proponents of these new developments cast their observations in a prolabor light. n return for their concessions, they point out, some unions have bargained for profit sharing, retraining rights, and job--security guarantees. Unions can also trade concessions for more say on the shop floor, where techniques such as quality circles and quality-of-work­ life programs promise workers greater control over their own jobs. Unions may even win a voice in investment and pricing strategy, plant location, and other major corporate policy decisions previously reserved to management. Opponents of these concessions from labor argue that such concessions do not save jobs, but either prolong the agony of dying plants or finance the plant relocations that employers had intended anyway. Companies make investment decisions to fit their strategic plans and their profit objectives, opponents point out, and labor costs are usually just a small factor in the equation. Moreover, unrestrained by either loyalty to their work force or political or legislative constraints on their mobility, the companies eventually cut and run, concessions or no concessions. Wage-related concessions have come under particular attack, since opponents believe that high union wages underlay much of the success of United States industry in this century. They point out that a long-standing principle, shared by both management and labor, has been that workers should earn wages that give them the income they need to buy what they make. Moreover, high wages have given workers the buying power to propel the economy forward. f proposals for pay cuts, two-tier wage systems, and subminimum wages for young workers continue to gain credence, opponents believe the U.S. social structure will move toward that of a less-developed nation: a small group of wealthy investors, a sizable but still minority bloc of elite professionals and highly skilled employees, and a huge mass of marginal workers and unskilled laborers. Further, they argue that if unions willingly engage in concession bargaining on the false grounds that labor costs are the source of a company's problems, unions will find themselves competing with Third World pay levels-a competition they cannot win. 想请问郭老师，这题opponents观点是在第三段，但是原文和选项要怎么对照呢...怎么从观点看出态度？

请问may老师 13) In triangle ABC, point X  is the midpoint of side AC  and point Y  is the midpoint of side BC . If point R  is the midpoint of line segment XC  and if point S  is the midpoint of line segment YC , what is the area of triangular region RCS  ? (1)   The area of triangular region ABX  is 32. (2)   The length of one of the altitudes of triangle ABC  is 8. 答案；A

求问此题：(3!+4!+5!)/(4!+5!+6!) =?

２１）Is │x - y│>│x - z│?（绝对值比大小思路？） (1)   │y│>│z│ (2)     x < 0 E 请问may老师

DS：求1/a+3/b等于多少？ 条件1：a和b的最大公因数是6 条件2：a和b的最小公倍数是120

请问老师，这题选项应该是A吧？谢谢！

一个立方体塑料盒内腔长宽高分别是x、y、zcm，塑料厚度是1，问塑料体积。谢谢老师解答！

求问此题：DS：K为正整数，问是否有超过3个的prime factor？ 条件1：K>30 条件2：K<20 很多人选A；我觉得应该选D;∵Prime Factors有：2/3/5/7……把最小的不同质数相乘=2*3*5=30；那么由条件一可得：K必然有超过三个以上的prime factors；有条件二可得K的不同质数必然只有2和3.所以俩条件都充分，请老师解答。谢谢！