例16， 假如数字变大，选出50本，不可能手算的，我的解题思路看右边， 4C1*6C1* 8C3， 为什么不能这么算？

麻烦郭老师看一下这几题，谢谢老师

麻烦郭老师看一下这几题，谢谢

请郭老师帮我看一下这几道题，好几个都完全不会…

请郭老师帮我看一下这几道题，好几个都完全不会…

不是很明白为什么A选项不对 我觉得outnumber了给其他人写信的数量可以作为这个period Emily写信的结果出现 为什么不能用现在分词呢？

麻烦郭老师帮我看看这几题，没写的或者标红的是完全没思路的，谢谢老师

请问陆旭老师！这里的pattern of number"8"是什么呢？！还有其他的pattern of 3之类的，都没看懂，类似的题目也不会做。谢谢老师指导！

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.

老师，我觉得这题条件1/2同时成立可以出结论。 因为条件二:X2＞XY，X2一定是正数，那么右边XY，Y＞0。所以X一定为大于0(因为一个正数不可能＜一个负数)。所以能推出结论选C.

想问一下金老师，句子最后加逗号后面有ed形式的非谓语动词，它的主语是不是可以是主句的主语，也可以是整个主句，还可以是离它最近的一套完整主谓宾的主语？还有如果是逗号加ed形式的非谓语动词在句子中间的话，是直接当做修饰前面的句子的主语还是离得最近的一个名词，还是后面句子的主语呢？