老师您好能否帮我讲解下下面这个文章考试时该如何读，我读完这种文章压根不知道在说什么，只知道在讲ocean basin形成机制的几种理论。No very satisfactory account of the mechanism that caused the formation of the ocean basins has yet been given. The traditional view supposes that the upper mantle of the earth behaves as a liquid when it is subjected to small forces for long periods and that differences in temperature under oceans and continents are sufficient to produce convection in the mantle of the earth with rising convection currents under the mid-ocean ridges and sinking currents under the continents. Theoretically, this convection would carry the continental plates along as though they were on a conveyor belt (conveyor belt: n. 传送带) and would provide the forces needed to produce the split that occurs along the ridge. This view may be correct: it has the advantage that the currents are driven by temperature differences that themselves depend on the position of the continents. Such a back-coupling, in which the position of the moving plate has an impact on the forces that move it, could produce complicated and varying motions. On the other hand, the theory is implausible because convection does not normally occur along lines, and it certainly does not occur along lines broken by frequent offsets (an abrupt bend in an object by which one part is turned aside out of line) or changes in direction, as the ridge is. Also it is difficult to see how the theory applies to the plate between the Mid-Atlantic Ridge and the ridge in the Indian Ocean. This plate is growing on both sides, and since there is no intermediate trench, the two ridges must be moving apart. It would be odd if the rising convection currents kept exact pace with them. An alternative theory is that the sinking part of the plate, which is denser than the hotter surrounding mantle, pulls the rest of the plate after it. Again it is difficult to see how this applies to the ridge in the South Atlantic, where neither the African nor the American plate has a sinking part. Another possibility is that the sinking plate cools the neighboring mantle and produces convection currents that move the plates. This last theory is attractive because it gives some hope of explaining the enclosed seas, such as the Sea of Japan. These seas have a typical oceanic floor, except that the floor is overlaid by several kilometers of sediment. Their floors have probably been sinking for long periods. It seems possible that a sinking current of cooled mantle material on the upper side of the plate might be the cause of such deep basins. The enclosed seas are an important feature of the earth’s surface, and seriously require explanation because, in addition to the enclosed seas that are developing at present behind island arcs, there are a number of older ones of possibly similar origin, such as the Gulf of Mexico, the Black Sea, and perhaps the North Sea.

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！