Good question.
This is an assumption question and there's a gap in the reasoning! The easiest way to narrow down the answer choices is to notice the new term in the conclusion - legislators proposing laws prohibiting behavior of actions that are only harmful to themselves.
On assumption questions, when there's a new term in the conclusion, it's not a bad idea to scan the answer choices and see how many discuss the new term. Answer choice (E) is the only one that ties this term back into the evidence and is the correct answer.
Evidence
1. Assumptions that appear to guide legislators will often become widely accepted.
2. Widespread acceptance of the idea is injurious to democracy.
Conclusion
If the legislators don't want to harm democracy, they should not pass laws prohibiting behavior of actions that are only harmful to those people engaging in the behavior.
Gap
If the legislators pass laws prohibiting behavior of actions that are only harmful to those people engaging in the behavior, then the legislators will appear to be guided by the assumption that individuals are incapable of looking after their own welfare. Best expressed in answer choice (E).
(A) is not assumed. The conclusion does not assume that legislators have favorable attitudes towards democracy.
(B) is an interesting play on the fact that legislators are typically considered prominent and powerful, but is not assumed.
(C) is the closest of the incorrect answer choices. But the last part about these legislators also appearing to value democracy is not required to establish the conclusion.
(D) is irrelevant. The argument is only regarding behavior that only harms the person engaging in the behavior, not behavior that also harms others.
Does that help clear this one up?
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