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.

这一题，主要区别在于by trying to与in trying to，为何in trying to好与 by呢？ 还有一个区别是划线最后的have had to与have themselves to之间的区别，为何这里不能用have themselves to呢？尤其是在划线前面已经出现了have themselves to的情况下？

没思路，不知道结合条件一及条件二如何得出X1的值...脑子不好使！

只能做到50的阶乘，乘以2的50次方，再加1 的结果 但是后面怎么思考就不清楚了，遇到这种题该如何去做，有什么直接的方法吗？

请May老师帮忙梳理一下这个题怎么用A排列或者C组合的方法算出答案，我每次遇到这种题似乎都有点毛病，不知道应该用A还是C还是结合...

条件一不是已经表明P是C的数量的两倍吗？而原文条件也说明了P或者C其中任意一个都可能为2/3的总量，而条件一表明P=2C 则总份额就是3C。C/（P+C）=1/3，可以得出答案啊，为什么不能选？

这题我认为主要考点在if与when的连用上以及consider后面接to be或者直接接noun。如果在BC选项it无指代可以排除，ADE三个选项中为何E是最优选项呢？这里情形我认为if和when都呢说得通，而且consider后面接noun或者to be在语法上没有问题。

这题正确选项E为什么which后面没有动词而是接的不定式形式，如果这样which后面就不是完整的句子了啊？

How many positive prime numbers are less than integer n? a) 14<n<20。 b) 13<n<17

这一题C，D两个选项中明显有一点不同就是一个用了but many scientist，一个用了and mant scientist. 从句意来看的话，这句话说了A提出了一个观点，但是很多科学家怀疑，然后转折P这个人之后测出来了。虽然D选项中P做的事情用过去时优于C选项中P用完成时，但我认为C选项连词用的比D好，为什么这题D选项优于C选项？