狒狒逻辑70（这数学题真邪乎）

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 

答案选B，可以理解，两个乘一乘，但问题是C有什么错呢，直接回答了原问题啊，难道他给了那个下雨概率就一定要用到？？

would be most useful for determine the probability that Plainville will have a thundershower soon.这个soon表明问的是即将到来的春天的雷阵雨的概率

 c说的是雷阵雨中的百分之几是由于这个气压导致的。这样暗含着雷阵雨发生还有百分之几不是由于气压原因导致的……也就是还有别的情况这样就没法算雷阵雨发生的概率了~~