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.

讲解

DS：已知9个数的平均数是43，求标准方差 1）最小的那个数是43 2）最大的那个数是43

一个数n的因子有2，3，5，n < 200，求n？ 条件1：4不是他的因子 条件2：9是他的因子

一辆火车走600 miles的路程，一般需要10h；火车中间走了一段速度20 miles的路；接下来是速度60miles的路，问速度60miles走了多久？ 条件1：速度20 miles走了3个小时 条件2：600 miles路程平均速度为56miles

一个数被10r整除，但不被10r+1整除，求r？ 条件1：这个数被25整除不被26整除 条件2：这个数被56整除不被57整除

数学考了一道，本来某一天下午两点水池剩n方水，每小时漏1/4方，每天下午一点会加进去14方，问水池剩m方的时候是星期几几点？

一个长方形长x宽y，能不能比较沿x边卷起的圆柱体体积和y边卷起圆柱体的体积？ 条件1：2x大于y 条件2：x小于3y

一个公司准备给一个地区中大于等于65，并且在当地呆的时间小于等于5年的人，发放谋谋福利，问这部分所占比例？ 条件1：该地区≥65岁的占比（某个值） 条件2：该地区呆的时间≤5年的人占比（某个值）

问x^y是否是odd？ 条件1：x是odd 条件2：可以求出来y是odd

编号1-8的蓝木板放到一个箱子里，编号1-8的红木板放到另一个。每个箱子各抽一块板，问抽到蓝木板和红木板编号一样的几率是多少？ 老师为什么不是 1/64?