求助牛人：一道关于概率的逻辑题！！！！！

soff

70. 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 determine 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 near by towns

我认为原文的意思是这样的：低气压时降雨概率是70%，低气压时会导致雷阵雨。

那么要想算出雷阵雨的概率，应该是低气压时的降雨率*降雨是雷阵雨的概率，这个相当于条件概率，因为不下雨就不能有雷阵雨，所以选B。而答案是C，答案上对C的解释是 低气压时的降雨率*低气压时的雷阵雨率，我觉得这个解释是矛盾的，因为你既然已经知道了低气压时的雷阵雨率还算什么低气压时的雷阵雨率啊，莫名其妙，直接就是结论需要的概率了啊，希望牛人给我指点迷津，谢谢

dingbo_009

我觉得跟条件没什么太大关系，它问得是从题目中你能得到什么信息。即下面的几个选项你能从题目中得到。提炼关键词B是 spring rainfalls   that are thundershowers从文中只能得到 spring, is the time of year in which thundershowers，和Plainville有没有关系不知道。而 thundershowers, which sometimes result from low-pressure systems, are most likely to occur （in Plainville）.能告诉我们thundershowers （in Plainville） that result from low-pressure systems。

maacid

当然是c

关键词是sometimes, 但是也有可能不是因为low-pressure system,所以要测

sasazan

C,其实和前面的70%没什么关系,目前已经是低气压了,那么只要只要低气压导致雷阵雨的概率就行了.

选B的话和这次会是雷阵雨的概率没有关系的.只是宏观的这地区一段时间的雷雨概率