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.

The profit from the sale of a certain appliance increases, though not proportionally, with the number of units sold. Did the profit exceed $4 million on sales of 380,000 units? (1)The profit exceeded $2 million on sales of 200,000 units. (2)The profit exceeded $5 million on sales of 350,000 units. 1不够，2 怎么看？ 谢谢

A report consisting of 2,600 words is divided into 23 paragraphs. A 2-paragraph preface is then added to the report. Is the average (arithmetic mean) number of words per paragraph for all 25 paragraphs less than 120 ? (1) Each paragraph of the preface has more than 100 words. (2) Each paragraph of the preface has fewer than 150 words.

PS ：给树标号，范围是201到740 某一品种的树的百位一定是4、5、6、7，个位一定是2、3、4、5， 求随便抽一棵树不是这个特定品种的树的概率？

DS：is|x-y|>|x-z|？ 条件1：是y的绝对值大于z的绝对值 。 条件2：是x<0。

1 3 2 B 3 4 4 10 A 2 8 1 第一列是调查的信用卡的拥有数，第二列是对应的人数，如第一行的意思就是三个人每人拥有一张信用卡，问信用卡拥有数的中位数？ （1）A=6 （2）B=7

m*(m+5)*(m+6)的因数可能是哪几个？ 3 ， 4 ， 6

连续四天股票收盘分别停在了8230，8390，8460，8530（数字可能有出入），第五天收盘多少？ （1）这组数的差值是220 （2）8390是这组数的中位数

三角形ABC，点D在AC上，D不能与AC相交（解释说这句话的意思是BD不能等于BA和BC，是独立的），AB是否等于BC？ （1）角BDC=角BCD （2）BD=DC

有A和B，共n个人（人数已知）他们每个人都可以同意或不同意一件事情，已知A有X人，B有Y人，bothA和B有Z人，求又是B又不同意的人？

给了两种书数量的比例3：X，求X？ （1）数的总数是15 （2）X小于13 讨论说选A，因为比例不能是3:12，必须要是最简形式1：4，可是我觉得3:12可以，3:2也可以，条件1不充分