小女子请教一道题

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.

可不可以请MM注明题目来源，下面贴子参考一下..
http://forum.chasedream.com/dispbbs.asp?boardID=24&ID=74827&page=1

这个也不是什么题库的题啦，就是我DOWN的一篇讲逻辑的文章里的例题。