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.

r/t=2? 条件1：点（r,t）在（0，y）和（x，0）这条直线上，x和y不记得了 条件2：点（r,t）过（0，4）和（3，6）

K P M是三个正整数，问KP+M是奇数吗？ 条件1：KM+P是奇数 条件2：PM+K是偶数

DS：x/a+y/b=1，求该直线与x轴的交点？ 条件1：b=3 条件2：a=b

PS：m,p都是正整数，p是质数。x2-mx+p=0这个方程的根是正数。求m-p的值？ 选项有1，2，4之类。

DS：有12个人给老师买礼物，每个人至少出一块钱，总共出的钱是否不少于30 条件1：有一半的人至少出3块钱 条件2：4个人出的钱至少是出钱最少的人出的钱的5倍

DS：定义F(n)=n/k的余数，问K>10？ 条件1：F(n+32)=6 条件2：F(n+42)=8

PS：一个国家telephone exchange numbers有七个digits，但前三个digits都是一样的数字，例都是932打头。问至少需要多少个数字(minimum required number)可以组成282000个telephone exchange numbers？ 选项是：三个2十几的数字和两个2百几的数字。

DS：a,b,c,d互不相等，(a-c)/(b-d)=a/b吗？ 条件1：a/b=c/d 条件2：(a+c)/(b+d)=a/b

PS：the value of （4^8 - 8^16）/（2^12 – 4^16）

PS：讲一个租赁汽车的公司每一次购买会购买5辆新车，每次卖掉会卖掉3辆旧车，今年新增了14辆车，把每次买和每次卖都算做一次交易，问今年最少做了几次交易？