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．
Reasoning: What additional information must be true for this conclusion to hold? Is it possible that different factors in different regions might reasonably account for the variation? Diseases or medical conditions for which these surgical procedures are appropriate might be more common in one geographical area than another．If the possibility of such geographical variations in the incidence of pertinent me(1ical conditions is ruled out，it is fair to conclude that the variation Can be attributed to unnecessary surgical procedures．
B Correct．This statement properly identifies additional information that eliminates the possibility that the geographical variation is due to legitimate factors.
og的解释丝毫看不懂，有没有好心的xdjm帮忙解释一下，谢谢
多谢，你的思路很清晰
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