Plz help me to understand the question stem. How geographical variation is related to surgical procedures?

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, prostatectomies, and
tonsillectomies are representative of surgical procedures in general.

Ans is B.

Thanks,
Ed