Help: A LSAT question

Layne

Although the ratio of physicians to total population is about the same in the United States and Canada, the United States has 33% more surgeons per captia. Clearly, this is the reason people in the United States undergo 40% 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 cometimes travel to Canada for certain kinds of surgery

D. General pracitioners 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

The answer is A. I could figure out it and got pretty confused by the answer. Thank you very much.

lawyer_1

原文推理：美国人均外科医生比加拿大多，所以人均手术比加拿大多。

A。如果美国人均需作手术的比加拿大的多，如美国人均需作1次手术，加拿大0.5。则人均手术多的原因不是美国外科医生多。A选项排除了这个可能。排除他因型。