I need help understanding why the correct answer choice (A) is correct for this question. I understand that all the other answer choices are terrible (leaving A as the only answer choice), but I still feel like A is too strongly stated to be a necessary assumption for the argument.
In my thinking, a necessary assumption for the argument is that the econ explanation and psychological explanation are mutually exclusive from each other. Answer choice A seems to go way beyond this and say that the econ explanation is excludes all other explanations (not just the psychological one).
What's wrong with my thought process? Thanks!