Respectfully, I disagree with the answer to this question. I'm not going to justify another answer--I just think the question needs to be revised (I know what source it comes from but I won't name names).
Put simply, this is a non-Official question where a lack of editing makes identification of the answer more or less just a guess!
I've made a video explanation here:
https://www.youtube.com/watch?v=OV7SwBP1S0IIn short, however, apply this:
a) IF we can assume that organic = better, this is viable -- ??
b) We're only concerned with the objective quality of the pizza; in any case it does nothing more than give us L = V, which is established in the argument NO
c) V is "not the best," implying that L = "not the best." DOES NOT, however, indicate lack of improvement (e.g., improvement from POOR to ACCEPTABLE) -- ??
d) Popularity of the pizza is irrelevant to quality -- out of scope. NO
e) Appetizers and desserts are not pizza -- out of scope. NOSo is the answer C or A? Depends on whether we choose to assume a) organic = better or c) that "not the best" is "not improved."
Neither one is a particularly good assumption to make. Flip a coin!
HOWEVER, if we could limit the logic in C to somehow imply NO IMPROVEMENT, e.g., "Valvano's is considered to be among the worst..." then it would be more correct. In short, the author tried to get clever with the double negation "not among the best" and tripped him/herself.
The moral of the story is to use Official questions for Verbal or risk confusion like this.