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.

为什么critique和envisioning不算并列？划线部分做同位语作用，为何不能用起伴随作用的DE？as well as是否既可以用在两者比较又可以用在三者？

请数学老师解答

请问数学老师 条件中 each more than 3 feet from the nearest wall 这个条件有什么用？再说下思路 谢谢老师

请问数学老师 条件2怎么可以快速推算结果

老师 我不太懂什么k一定是4的倍数呢？

ken老师这道题目答案对吗？为什么说两个条件中的方程是同一个方程啊，我算出来不一样，当条件1&2同时存在时，两个方程是有两个交点，应该就是可以判断出（a,b)的值吧？

请问数学老师 这个题如何在短时间内快速得出答案

ken老师 这道题目黄色部分我不太明白，An和n各自代表什么意思？我以为An代表的整数列所有数的合，那n不可能小于100呀，好奇怪

麻烦金老师回答，主要的困惑在于AB两个选项。一个that位置的不同，和will 和 would 的不同。刚开始我的思路是旅客会更多的使用旅行机构这件事是一个预测，没发生的，虚拟语气所以就错选了B.will 和would 的区别是 will 表达的感觉更确定一点吗？

麻烦金老师回答，这题看到DIGGING 这个动作是人发出的 不可能是化石发出的，排除AB ，C 里面的it 指代不是很清楚。对比DE， 这个化石来自那里这个部分的内容比较长所以D 选项是用了一个从句来说明的意思吗？就是关于DE选项的appears 和 APPEAR 这个差一点我不是很清晰，还是说D这个答案的what 这个选项引导的从句直接修饰到bones上，所以胜出？