feifei-70再看觉得应该选B，请问大家的意见

xinxinokkk

括号里是我的理解～希望大家讨论喽～

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(B)
“详解版”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。

(得不出，应该还是是B 对。文中说春天是雷雨高发季，且雷雨有时是低压导致，是推导的前提。接着说70%的低压天气导致降雨，但降雨与雷雨之间缺乏桥梁，因此B正确。C项是雷雨是低压导致的概率，但并不等于低压导致雷雨的概率。比如，可能有50%的雷雨是低压导致的，但低压可以100%导致雷雨，只不过还有别的原因会导致雷雨，所以前者没有100%的概率)

demonlin

根据原文意思
1.70%的低气压导致降水
2.低气压会导致雷雨
问：雷雨发生的可能性

可不可以这样理解rainfall 这个词 它是降水的意思 而雷雨是一种降水类型
所以逻辑链里面缺少了一环
低气压导致降水的比率*雷雨占降水的比率=低气压导致雷雨的比率
所以选B

feifei后面的答案是B 解释里面答案变成C了
而且有好几题题目里面都有错误
应该更新修正一下了。。