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.

请唐塘老师分析一下这道题，谢谢

想问下may老师什么时候变化率的计算公式 什么时候分母是被减数，什么时候是减数 像这题求时间的变化率分母是距离也就是被减数，但是对于其他年增长之类变化率的分母就是减数，想知道这个区别，谢谢老师

请文静老师解答：老师我读主旨大概总结为：各个政府开出优惠政策来吸引商家只会两败俱伤，这样不会创造更多的就业岗位，只会影响工作的布局。觉得B很核心的反应了文章主旨。因为从文章主旨上读出这样的行为各个政府都不受益只是影响工作布局罢了，那为什么政府还要重点关注E里竞争者开的条件呢？

老师您在讲课的时候把总数设为了a,将有副作用设为y,将有疗效设为了x,那通过条件（1）就可以知道有疗效为0.9a,没有疗效为0.1a,但是是怎么得出“没疗效有副作用”也为0.1a从而结合题设把y用a的式子表示的呢？感觉只能得出T这一栏里“没有疗效”的总数为0.1a哇

想问下may老师这题怎么做

想问下may老师怎么做

想问下may老师怎么做

[急] 这题七龙珠答案给的C，但是这里的contemporary只能是形容词或者名词，是不是不能直接接在名词后面用？如果这是个硬伤的话，E会不会更好一些呢？

[急] 请问May老师，这里通过连接下面圆的圆心，是不是是不是可以得到r跟b的直接关系，这样选A是不是就可以了呢？

当时老师讲的答案是A。statement 1 sufficient；statement 2 not sufficient。但是我现在不太理解了，觉得答案有些问题，能不能再详细的讲一下这道题怎么做？谢谢！