费费逻辑70 请教

modernre

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
大家帮忙看下这道题目，答案说是C，但是我觉得是A，因为题目中说 thundershowers, which sometimes result from low-pressure systems，只是说SOMETIMES,也就是说有的时候thundershowers不是由Low-pressure systems，而题目中要我们估算the probability that Plainville will have a thundershower soon，也就是general的thunderhower发生的情况，如果是这样的话，A的答案不是最直接吗？

vakaka

Agree with B.

Steven0124

A) the percentage of thundershowers in Plainville that occur in the spring

This percentage is:
(# of T-storm in spring)/(# of T-storm in the whole year) in Plainville

modernre

Could you pls explain B to me? And I have put forward my thought for option A, could you pls have a look at it and make some judgement for it?

Thx

Steven0124

B is the choice.

kenwk

The answer is B