OG10-172题目读不懂！！！郁闷半天了！

172. There is a great deal of geographical variation in the frequency of many surgical procedures—up to tenfold variation per hundred thousand between different areas in the numbers of hysterectomies, prostatectomies, and tonsillectomies.

To support a conclusion that much of the variation is due to unnecessary surgical procedures, it would be most important to establish which of the following?

(A) A local board of review at each hospital examines the records of every operation to determine whether the surgical procedure was necessary.

(B) The variation is unrelated to factors (other than the surgical procedures themselves) that influence the incidence of diseases for which surgery might be considered.

(C) There are several categories of surgical procedure (other than hysterectomies, prostatectomies, and tonsillectomies) that are often performed unnecessarily.

(D) For certain surgical procedures, it is difficult to determine after the operation whether the procedures were necessary or whether alternative treatment would have succeeded.

(E) With respect to how often they are performed unnecessarily, hysterectomies, B
        prostatectomies, and tonsillectomies are representative of surgical procedures in general

这道题我选的是正确答案B， 根据直觉选的， 但是题目的逻辑意思至今都弄不懂！！什么geographical variation 在frequency 里啊 ？怎么地理这差别和频率有什么关系啊？ 这题意思不是在治病吗？

有哪位好心人帮我翻译一下整个意思啊？ 谢谢拉！！ （从来没有为自己的阅读能力这么自卑过！

geographical variation in the frequency of many surgical procedures的意思是 很多外科手术执行的频率随着地理位置的变化而变化，即有这种可能：同样的一种手术，在这个地方很少执行，而另外某个地方，却有很多的病人接受了这种手术。后面还附了三种手术的例子，手术H,P,T在不同地区之间的执行频率有高达十倍的差异。

恩 谢谢！明白了