A low-pressure weather system is approaching Plainville; rainfall results from about 70 percent of such systems in the LACE w:st="on">PlainvilleLACE> 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 LACE w:st="on">PlainvilleLACE>.

Knowing which one of the following, in addition to the information above, would be most useful for determining the probability that LACE w:st="on">PlainvilleLACE> will have a thundershower soon?

(A) the percentage of thundershowers in LACE w:st="on">PlainvilleLACE> that occur in the spring

(B) the percentage of spring rainfalls in LACE w:st="on">PlainvilleLACE> 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（B）

(E) whether Plainville has more or fewer thundershowers each spring than do nearby towns

请问答案到底是B还是C? 我的资料上一个说是B, 一个说是C 而我觉着它们两个都对 请帮忙指点一下推理过程, 谢谢!

原文：现在低压天气正靠近。70%低压天气有rainfall。现在正是spring

B。spring rainfall的百分之多少几率是thundershowers。这样就知道了thundershower的可能性。

C的意思为thundershower百分之几可能性来之于低压天气。如果改为低压天气的百分之几可能性产生thundershower。则为答案。请细心体会其区别。关键看percentage修饰那个。