请问NN OG 11th 紫色 53题

happywawa

53．There is a great deal of geographical variation in the frequency of many surgical procedures—up to tenfold variation per hundred thousand people among 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，prostatectomies，and tonsillectomies are representative of surgical procedures in general．

答案为B

题目又没有看懂，还请NN帮忙解释一下

woodsender

题目大概的意思是在许多外科手术的变换中产生了很多的变种variation，在hysterectomies, prostatectomies, and tonsillectomies中特别多，多达10倍。问加强这些变种是由于不必要的外科手术产生的原因？B选项排除他因，说变种不和其他因素（除了hysterectomies, prostatectomies, and tonsillectomies）有关系。

happywawa

geographical variation

up to tenfold variation per hundred thousand people among different area

怎么解释啊？