想来想去想不通，帮忙分析一下解题思路

majun

19. Although the ratio of physicians to total 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 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 who is a candidate for surgery before sending the patient to a surgeon.

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

mingming8152

我选c

分子分母的关系

edmundshi

我选A

逻辑链：医生和总人口的比例一样的前提下 美国比加拿大多33%的外科医生是美国人均手术比加拿大多的原因

A的意思是美国人对外科手术的需求小于等于加拿大人对外科手术的需求

实际加强了结论，assumption题我都当成加强题做的

xfi883

楼上分析得没错。补充一下：

C说“有些美国人会去加拿大治病”，那么结果就是——加拿大的医生更不够用，美国的医生更富余——导致美国比加拿大的医患比更高。所以错误。

相同，A的意思是说：美国人不会增加更多的病人了，那么医患比保持稳定，所以正确。