PharmaCorp, which manufactures the drug Aidistan, claims that Aidistan

Hi Sajjad, I always get your questions wrong.. Why is that??

Because the quested posted or not up to the level of GMAT standards. Many of the posted questions are from unrecognized sources. Try to solve question from recognized sources such as Manhattan and OG.

I have few clarifications here:
1. You state the Assumption as following:
This argument relies on the assumption that Gregg’s Syndrome is more prevalent among Puma Syndrome victims who take Betatol than among those who take Aidistan.
My understanding of the question stem:
Premise 1: PharmaCorp (PC) claims its drug A is more effective in treating Puma Syndrome than is drug B.
Premise 2: PC states a Stats fact --> 1/2 successful cases for drug A whereas 1/3 such cases for drug B. Both used alone.
Premise 3: Gregg's Syndrome has been known to render PS more resistant to any treatment.
Conclusion: PC's claims cannot be taken seriously.
Nowhere in the Question stem mentioned implicitly that Gregg's syndrome is more prevalent among Puma Syndrome victims, who take Betatol

2. Rest of the explanation aligns more with C than with A. C states that Gregg's syndrome is indeed a factor, and that nullifies the effect of A more than effect of B. So in the presence of Gregg's Syndrome, PC cannot claim that its drug A is better than B. Though somewhat murkier, option C could not be eliminated.

On the other hand, option A neither supports nor weakens the conclusion. It states that for people with both GS and PS, fewer are treated with A than with B. Question stem states it renders any drug ineffective. So does the #people treated matters? Of course, we can assume that it is because drug A is less effective when both syndromes are present. But that's what option C says.

Can you help me where I am going wrong?