I understand that C is true and is a flaw in the argument, but I still don't understand how you can eliminate A. Here is my breakdown:
Generally, professors grew up in economically advantaged homes (MP). Evidence of this is the fact that professors grew up in communities with average household incomes that were higher than the national average.
What I am looking for: The argument makes a whole to part flaw. Did the professors actually live in the higher income households in the community? What if they only lived in the low income households? This could be true since we are only given an average of the income in the communities. Also, does household income being higher than the national average mean economically advantaged? I am not so sure. High household income is just one part of "economic advantage;" there could be other economic things such as government policies towards rich people that can nullify the high income advantage. In other words, there are a ton of factors that go into defining "economic advantage," not just income.
Answer A: I don't see how this is incorrect. Isn't this pointing out the flaw that "high household income" might not actually mean "economic advantage?"
Answer B: This is consistent with the argument due to the word "generally" in the passage.
Answer C: This is definitely a flaw in the argument since it points out the assumption that the professors actually lived in the "good" households in the community.
Answer
Who cares about the private sector?
Answer E: Who cares about where they live now. We only care about where/how they grew up.
Comments
This is a very hard question, and I have read through A a few more times; my only reasoning for eliminating it is the fact that the argument doesn't really establish a correlation between the two (this still seems odd since the argument is causal, and for there to be cause, there must be a correlation at least). Other than that, I got nothing.
I agree that your rephrase of answer A would probably be enough to turn it into a correct answer choice.