怎么也想不明白的一道题，求解。 CXD assumption-30

Although the ration of physicians to total population is about the same in US and canada, US has 33% more surgeons per capita.Clearly, this is the reason people in US undergo 40% more operations per capita than do Canadians. The explaination given above rests on an assumption that:



A, patients in US do not have a greater need for surgery than do patients in Canada.

B, the population of US is not larger than that of Canada.

C, US patients sometimes travel to Canada for certain kinds of surgery.

D, general practitioners in US 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.

答案是A。我怎么也想不明白，请各位前辈指点思路。

美国人均外科医生多是因为美国人均operation多

A答案排除了可能导致美国人均外科医生多的另外一个原因surgery多，所以可以认为assumption

做Denial test,如果美国人的surgery多，那么美国人均外科医生多可能是因为这个原因，而非文中提到的原因了，所以我觉得A可以作为assumption