请教OG172 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,
prostatectomies, and tonsillectomies are representative of surgical procedures in general.

the key is b

请问各位这道题目如何理解，思路怎样的, 谢谢先

原文：不同地区的手术程序变化程度大大不同，甚至在H，P，T病的手术程序方面，不同地区的每10万个手术，变化程度的差异达10倍。比如，在A地区，每10万个H病手术中，有10种不同手术，在B地区，可能有100种不同手术。

结论：这种差异是不必要的

答案：B说这种差异和手术必须的因素无关，即和影响疾病的发生的手术应考虑的因素无关。

谢谢斑竹！！！！

我的理解是:不同地区的frequency of many surgical procedures不同--就是说这3种病的任一种病在甲地区要做n此治疗但在乙地区要做10Xn此治疗

那种理解对做题影响不大

我理解FREQUENCY 是指手术的频率,也就是说这三种病可做手术或不做手术,不同地

区不同

如果这个地区普遍不建议做手术治疗这三种疾病,那么频率肯定低,原文要我们支持:

地区手术频率的不同的唯一原因是由于不必要的手术造成的,所以用排除他因法