Although the ratio of physicians to toal 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.

The explanation given above rests on an suumption that

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 candidate for surgery before sending the patient to a surgeon

e there are no unnecessary surgical operations performed in Canada.

Answer is A.

I was totally confused by the this choice, and did not identify any comparisons mentioned in A.

这题的推理过程是这样的：

米国和加国的医生比例一样，但米国的人均挨刀子的比例比加国多33％，因而米国人比加国人要挨40％多的刀子。

A）是一个典型的排除他因。

B）如果取非，实际上对结论的加强，肯定不对

C）无关

D）提干没有讲过practitioner，无关

E）与A一样，取非后是对结论的加强

个人意见，仅供参考。