同学们有空来检验下自己的逻辑题，谢谢

changchangz

源自费费，我觉得答案给错了，应该是B选项才对，大家觉得？

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

参考答案：C
思路：文中给出两个条件，1是低压天气将到达，而70%的低压天气导致降雨，2是现在正是1年中雷阵雨最多的季节且雷阵雨有时也是由于低压天气导致；答案（C）给出了低压天气导致雷阵雨的比率，用70%乘以这个比率，就可以得到下雷阵雨的概率了。
A、B没能和低压天气联系起来，D、E为无关选项

x_fan

B知道了春季降雨中是雷雨的概率
但是原文根本就没有给春季降雨的概率，给的是在低压系统下降雨的概率。
所以B肯定不对。

fanbiyuncat

我也选的B,很迷茫……呜呜，快要考试了，突然发现不行呀……

oo1x1oo

同有疑惑。。。我也选的是B。。但看看C也是对的。。。。求指导

x_fan

前提：
1、低压系统正在靠近
2、70%的低压系统——〉降雨
3、有时低压系统——〉雷阵雨，特别是春天容易发生

结论：
即将有雷阵雨的概率可求得。

找它的假设：
显然如果知道了 低压系统——〉雷阵雨 的概率，就足够了。
A没提到低压系统。
B强调了春天，而文章的前提是低压系统而不是春天的低压系统。
DE无关。