CXD PAGE48 NO.30

CXD的第PAGE48 No.30

30. Although the ratio of physicians to total population is about the same in the United States and Canada, the United States has 33 percent more surgeons per capita. Clearly, this is the reason people in the United States undergo 40 percent more operations per capita than do Canadians.

A)     patients in the United States do not have a greater need for surgery than do patients in Canada.

B)      The population of the United States is not larger than that of Canada

C)     United States patients sometimes travel to Canada for certain kinds of surgery

D)     General practitioners in the United States do not as a rule examine a patient who is a candidate for surgery before sending the patient to a surgeon

E)      There are no unnecessary surgical operations performed in Canada

这道题的正确答案是：A，可是，为什么B，C不对呢？这道题，自由比较晕，不知道怎么分析这个题目，谢谢大家提供一些比较好的假设题目的思路，结合这个题，最好把5个选项的对和错帮忙分析一下，谢谢大家的宝贵思路。感谢！

题目是：美国的外科医生多导致了外科手术多。

题目基于假设A。如果A不成立，那就推翻了题目推论，也就是说美国外科手术多不是由于外科医生多导致的，而是由于病人多导致的。

B美国人口和加拿大人口的多少和题目推论是否成立无关。美国人口多并不代表需要做手术的病人多，反之亦然。

C，D，E，取非原推论仍然肯呢个成立。假设是要找原推论成立的必要条件，C,D,E都不是必要条件。