求证答案一道

．Although the ratio of physicians to total population is about the same in the United State 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 assumption 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 a candidate for surgery before sending the patient to a surgeon.

(E)there are no unnecessary surgical operations performed in Canada.

是d吗？感觉怪怪的．．．平均每个美国人开刀的次数多是因为医生开刀的次数多？题目读起来就很奇怪

答案是A。

题目说美加内科医生的比率一样多，但外科医生美比加的比率高。结论是，因此美比加多40%的手术，即手术多的原因是外科医生多。

一种假设是不是因为美国病人本来就更需要手术，也就是A说的。如果把A取非后就会削弱原命题。