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.

数学：请问老师这道排列组合怎么解 感觉好复杂

老师，请问这道题思路是什么？

老师，求该题解题思路

DS：说一个女生有一些 tax deductible 其中捐给 b 让她少交了 210 的税，问什么忘记 了求补充，好像是她总收入是多少？ 条件 1：给了税率是 28% 条件 2：给了可税工资（income-deductible）是个五位数。 income*0.28-（income-deductible）*0.28=210 构筑纠结很久 因为题里面说捐给 b 只是 deductible 其中一项，还有其他未知，所以最 后选了 e，现在感觉选 c 请问陆老师，应该选什么？谢谢！

DS：n 是三个不同质数的积，这些质数都在 1-15 之间，问 n 是否＜700？ 其中一个条件是 n 与 70 没有公约数 【补充】 DS：x,y,z 是三个质数，xyz<700？ 条件 1：三个数不大于 14 条件 2：三个数里面有 70 的因数 s 轩辕十四 12/20 【122-补充】 DS：三个整数，问他们的积和一个常数的关系 条件 1：都是小于 15 的质数 条件 2：是 30 的 factor 构筑：这个好像也是个变体吧，好迷啊 ggggggbbbbbb bb 12/20 【122-补充】 DS：Integer p: is p>700? 条件 1：p is product of three prime numbers from 1-15 条件 2：p has no common factor with 70 请问陆老师，这道题选什么？谢谢！

DS：2x^2+bx+8=0，只有一个实数根，求那个字母的值？ 条件 1：b<0 条件 2：lxl>5 x的绝对值 请问陆老师，这道题选什么？谢谢

想请教一下陆老师，我觉得这道题应该是用相似三角形做，看了图觉得应该是用角1和角2相等来证明。但是由题干给的条件，我不知道如何得出角1和角2相等

请问老师图里的这道语法比较，不太明白，如何区分到底比较的是什么呢？谢谢

请问May, 我这道题不知道怎样做？谢谢！

请问May老师，请问这题选5 吗？