I chose E and I think that is because I think when I was doing the PT I approached this questions more like a necessary assumption question than a strengthen. Can someone explain why E is wrong though; is it just that C is better/stronger?
As for C, I see how the argument James made works for that answer choice and I agree conflation of outcomes with opportunity will be problematic on this question. One issue below though:
James Finch wrote:
Premise: Economic inequality bad for democracy
Premise: Economic expansion leads to more economic opportunity
Conclusion: Democracies should promote economic expansion
However, the first premise is that "segmentation into classes of widely differing incomes
between which there is little mobility" is bad for democracy. If you are missing the underlined part then yes that would just be inequality but since that part is there in the stimulus, the sentence clearly reads that the lack of of income mobility is the issue.
Then, the stimulus goes on to establish that economic expansion provides "people more opportunities to improve their economic standing." This second premise provides solid support for the conclusion that democracies should promote economic expansion and you do not need to prove that economic expansion actually results in solving inequality of outcomes (answer choice C). I definitely see how C strengthens the argument but not quite required as James said.
For E, if we add this as a premise then I think we also help the conclusion that democratic societies need to promote economic expansion. Adding this to the first sentence results and we get: the divisive political factions that result from a lack of mobility threaten economic expansion are an additional obstacle to economic expansion itself. This is a positive feedback loop, albeit for a negative outcome. Thus. we need the democratic society itself to adopt policies that ensure economic expansion so we avoid this positive feedback loop.
I'm not trying to state a personal opinion here but real-world examples help and I think this fits almost perfectly with Jerome Powell's recent comments / reasoning for a likely upcoming cut to interest rates. He's saying we should adopt (or rather, he'll enact) a policy to ensure economic expansion so that people have more opportunity to improve their economic standing, such as through low interest rate loans to go to law school or get a car/house/business/etc.