https://classic.7sage.com/lsat_explanations/lsat-52-section-1-question-25/
From a common sense stand point, the necessary assumption makes sense.
So because blah blah is injurious to democracy, then legislators should not do something. Why should the legislators not do something? Because it is injurious to democracy.
So if the legislator does do that “something,” then it is blah blah injurious to democracy.
But what is the correct way to diagram using logic?
A -> -B.
B -> -A? (But this can’t be right, because “-A” would mean that blah blah is not injurious to democracy…
For #24, I think that even with the absence of the word "all", the answer choice would still be wrong. It was only the "rare varieties" (Line 19) that experienced wild swings in prices. In fact, lines 22-23 states that common bulbs were actually sold for very low prices during this time period.