注意C并不能推出spring 的 thundershower probability, 它可能是全年的结果。 而由B我们可以从lowpressure * 70%--->rainfall possibility + B中条件(spring rainfalls that are thundershowers)----> the possibility of spring thundershower rainfalls under lowpressure weather system.
以下是引用gracehu在2003-11-29 10:17:00的发言:21. A low-pressure weather system is approaching Plainville; rainfall results from about 70 percent of such systems in the Plainville area. Moreover, the current season, spring, is the time of year in which thundershowers, which sometimes result from low-pressure systems, are most likely to occur in Plainville. Knowing which one of the following, in addition to the information above, would be most useful for determining the probability that Plainville will have a thundershower soon? (A) the percentage of thundershowers in Plainville that occur in the spring (B) the percentage of spring rainfalls in Plainville that are thundershowers (C) the percentage of thundershowers in Plainville that result from low-pressure systems (D) whether low-pressure systems in other areas are associated with rainfall (E) whether Plainville has more or fewer thundershowers each spring than do nearby towns The answer is B! Why not C? Thx in advance for any explanation [此贴子已经被作者于2003-11-29 10:23:29编辑过] |