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.

PS：问49.987*9.879／0.253化简结果最接近哪一个？ 选项a.b.c忘记了，d是1700，e是1800

数学书60页32题，有多少小于20的正整数等于3的正倍数与4的正倍数只和，答案说10个，我怎么查都是11个

PS：一个数是两位数，这个数大于11，个位数和十位数加起来的和是质数，问这样的 数有多少个？

57)If m is a positive odd integer between 2 and 30, then m is divisible by how many different positive prime numbers? 1)m is not divisible by 3. 2)m is not divisible by 5. 条件1 我理解的是 M 只能2到30之间，那么就有5，7，11，13，17，19，23，29，这么多个prime numbers. 条件2 我理解的是 M 可以是 3，7，9，11，13，17，19，21，23，27，29 这些，21可以被3和7除， 我判断条件1完全可以，条件2 我不太确定

62)if d is the positive integer and f is the product of the first 30 positive integers what is the value of d? (1) 10d is a factor of f. (2) d > 6 这个题目说d 是一个正整数，f 是30！阶乘，d的值多少， 这个题应该怎么推理？

DS：说一个整数N，最大不超过50，把从1到N的所有数拉出来列一起，数字里出现4的数字有几个？ 条件1：这些数里出现0的个数是出现4的个数的数字少11； 条件2：说N这个数是某个prime number的平方

错选了D，麻烦老师分析一下这题的时态！

错选了最后一个，麻烦老师讲解一下！

老师麻烦讲解这道题 Making things even more difficult has been general market inactivity lately, if not paralysis, which has provided little in the way of pricing guidance. A has been general market inactivity lately, if not paralysis, which has provided B there is general market inactivity, if not paralysis, lately it has provided C general market inactivity, if not paralysis, has lately provided D lately, general market inactivity, if not paralysis, has provided E is that lately general market inactivity, if not paralysis, which provides

讲解～