请教Metro City has a lower percentage of residents with humanities degrees题

BloomPower

原题如下：
Columnist: Metro City has a lower percentage of residents with humanities degrees than any other city of comparable size in our nation. Nationwide, university graduates generally earn more than people who are not university graduates, but those with humanities degrees typically earn less than do graduates with degrees in other disciplines. So the main reason Metro City has higher income per capita than any other city of comparable size in our nation must be its low percentage of residents with humanities degrees.
.
Which of the following, if true, would most strengthen the columnist's argument?
.
A. Metro City residents with humanities degrees have higher income per
capita than do people with humanities degrees in any other city of
comparable size in the nation.
B. The percentage of residents with university degrees is lower in Metro City
than in any other city of comparable size in the nation.
C. Nationwide, university graduates without humanities degrees typically
earn more than do individuals without university degrees.
D. Metro City residents with degrees outside the humanities have per capita
income no higher than the per capita income of such residents of other
cities of comparable size in the nation.
E. In Metro City, a lower proportion of university graduates have humanities
degrees than in any other city of comparable size in the nation.



正确答案为D

错选：B

思路：题型为strengthen
结论为：the main reason Metro City has higher income per capita than any other city of comparable size in our nation must be its low percentage of residents with humanities degrees.

its low percentage of residents with humanities degrees--> higher income per capita than any other city of comparable size in our nation

类型应该是果因推理，下意识想排除他因

又看到
Nationwide, university graduates generally earn more than people who are not university graduates, but those with humanities degrees typically earn less than do graduates with degrees in other disciplines.--->特别是前半句

想到其他原因可能是：Metro city中，非大学毕业的人少，大学毕业的人多，所以人均收入多

发现选项B：
B. The percentage of residents with university degrees is lower in Metro City
than in any other city of comparable size in the nation.

排除了这个他因，因此选了B。

之后又看到了D，又纠结了一下，感觉两者都排除了他因，但B和文本内容结合地更紧密，所以选了B。

请教一下各位大神，我的思维哪里错误了，哪里有待改进，多谢。

BloomPower

啊，自顶一下吧，逻辑区感觉比较冷啊~

长丝弓

题干首先大学生是高收入人群，要靠大学生收入占比高，才能拉高全城人均收入；在大学生的pool里，文科生的收入<非文科生的收入 （注意啊，文科生在大学生里头收入相对少，可没说文科生收入<非大学生收入）
B选项（高收入人群）大学生比例小，人均收入哪高的起来？是趋向削弱

思路：
首先大学生收入是主力，大学生收入在总人口收入占比是不能低的，
简化一下问题：考虑大学生pool里，大学生人均收入=文科生人均收入*文科生比例+非文科生人均收入*非文科生比例=文科生人均收入*文科生比例+非文科生人均收入*（1-文科生比例）
作者假设：
M城人均收入高，大学生人均收入是不能低的，
文科生人均收入相对较低，文科生比例也低，那么文科生人均收入*文科生比例是低的，非文科生人均收入*（1-文科生比例）就不能低了，
这里两种可能
一种是靠非文科生人均收入拉高，那非文科生比例（=1-文科生比例）可以低一点，即文科生比例可以高一点，那就没有体现文科生比例低导致全城人均收入高的作用
另一种是非文科生人均收入也不高，M城人均收入要高，得靠非文科生比例（=1-文科生比例）拉高。这时文科生比例非低不可，符合题干文科生比例低导致全城人均收入高的结论，是支持，选项D体现了这一点，正确

BloomPower

长丝弓 发表于 2021-9-20 18:43
题干首先大学生是高收入人群，要靠大学生收入占比高，才能拉高全城人均收入；在大学生的pool里，文科生的收 ...

感谢您的回复
但您所说“首先大学生收入是主力，大学生收入在总人口收入占比是不能低的”是您自己附加的一个新的assumption
而我认为，您构建这样一个assumption，其实说明了另一种可能存在的情况：

只要Metro City的大学生占总人口的足够多，即使文科生的比例更高，且其他学科人均收入与其他城市类似，Metro City仍然可以有更高的人均收入。

但在您的讨论中
您实际上默认一个assumption：所有比较的城市都有类似比例的大学生人口了
而这正是B的选项所排除的他因（B本身的大学生人口比例比其他城市高，所以人均收入高）

长丝弓

BloomPower 发表于 2021-9-23 11:22
感谢您的回复
但您所说“首先大学生收入是主力，大学生收入在总人口收入占比是不能低的”是您自己附加的 ...

这个不是假设，是题干给定的信息
Nationwide, university graduates generally earn more than people who are not university graduates