PT20.S1.Q20 - some people have been promoting a new herbal mixture

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http://7sage.com/lsat_explanations/lsat-20-section-1-question-20/
I got this question correct since C was obviously not relevant to the argument, but during BR, I can't seem to eliminate B or E. Why are these necessary assumptions? Here is my breakdown so far:

This is a necessary assumption EXCEPT question. Specifically, we are looking at the skeptic's argument.

Some people have been promoting some herbs to help treat colds. The herbs have a whole bunch of colorful sounding stuff in them: purple coneflower and goldenseal. This dude with a cold doesn't think that the herbs help. He argues, "Say that the herbs actually did work. Most people want to get better quickly. Therefore, almost everybody with a cold would already be using. Since there are many who have colds but don't use it, herbs aren't effective."

What I am looking for: I know we are looking for a NA, but I always like to break down the flaws in the argument if there are any. The skeptic is all over the place. He conflates "most" with "almost everybody." Certainly "most" includes "almost everybody," but 51% is "most" but would probably not be considered "almost everybody." Additionally, so what of "many" people still have colds? The proponents of herbs never said that herbs have a 100% effectiveness rate. Even worse, the skeptic's conclusion is borderline circular as well. The skeptic says that "almost everybody would be using it." He did NOT say that everyone would use it; there could be "many" or "some" people that don't use the herbs in the skeptic's hypothetical world. Anyway, we are looking for an answer that is a necessary assumption.

Answer A: This is a NA. If this answer was not true, then how could almost everyone be using it? There wouldn't be enough.

Answer B: I don't see how this is a NA. If you negate it: the mixture does have side effects severe enough to make many people with colds avoid it, then how does this wreck the argument? Wouldn't this strengthen the argument's conclusion that the herbs are not effective? The negation seems to do the opposite of wreck the argument.

Answer C: This is what I correctly chose because the argument does not concern itself with anything preventative. This answer does nothing to the argument, and it is totally irrelevant.

Answer This is similar to A, and it is a NA. If you negate it: if the herbs are not widely known, then how would people know to use it?

Answer E: This is like answer choice B for me. I don't see how this is a NA. What if there are effective cold remedies that people prefer? Does this mean that the herbs are not effective? I don't see how this affects the argument.

c.janson35

Your discussion of the argument is a very good one, and the mindset you bring to the questions is definitely going to help you with the test, so good job on that!

I don't think the flaw of the argument is necessarily the most/almost everyone conflation that you described. Rather, the problem with the argument is that it is assuming that just because a cold remedy is effective it would necessarily be in wide usage. But this is a huge assumption to make, and there are A LOT of gaps to be filled here, which makes sense because this is a NA Except question. All of the incorrect answers hinge on this relationship.

B: if the mixture had side effects severe enough to deter people from using it, then the conclusion would be severely weakened because it's basing its judgment about the ineffectiveness of the remedy on the fact that it's not widely used. But if the reason why people aren't using it is because it has severe side effects, then it still may be effective! The relationship between the conclusion and premises is destroyed.

E similarly fails in this manner. If there were another drug that more people preferred, then the remedy's unpopularity could not be held as an indicator of its efficacy.