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?

• AA local board of review at each hospital examines the records of every operation to determine whether the surgical procedure was necessary.  
• BThe variation is unrelated to factors (other than the surgical procedures themselves) that influence the incidence of diseases for which surgery might be considered.  
• CThere are several categories of surgical procedure(other than hysterectomies, prostatectomies, and tonsillectomies)that are often performed unnecessarily.  
• DFor certain surgical procedures.it is difficult to determine after the operation whether the procedures were necessary or whether alternative treatment would have succeeded.  
• EWith respect to how often they are performed unnecessarily, hysterectomies, prostatectomies, and tonsillectomies are representative of surgical procedures in general.