求助 狒狒逻辑 70题

eeheaven

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

答案是c  
个人怎么觉得是b啊  知道70%的低气压导致降雨  又根据b知道降雨中雷阵雨的概率   相乘不就是结论吗    希望大家给点帮助 完分感谢

seuhongkai

Not all rainfalls come from low-pressure weather system.

zm_patrickS

这道题目实在不明白，为什么选C呢？
C说雷阵雨里面多少由低压导致，怎么能推出结论呢？不明白啊，NN们快来啊～

saharaa

同问~我也选的B~
rainfalls的概率*thundershowers占rainfalls比率=答案
怎么想怎么是B~
选c就没rainfalls啥事儿了~
为什么啊~答案有问题吧！

alicejingli

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.

问的是由low-pressure systems 导致的thundershowers。不是问rainfalls中有多少thundershowers。
有可能rainfalls还不是由low-pressure systems 导致的呢。