On page 58 of All the Verbal, there is an example provided below:
"Researchers discovered that the most common RISK FACTOR resulting in cholera epidemics is the LACK of a clean water supply."
I see that the adverb "most" refers to "common", so this is an adverbial modifier.
However, the book does not mention if "common" is in itself an adverb because it is describing the noun risk factor? To confirm, is what I just said correct? Is this a double whammy where you have two adverbs "most" and "common"? Can an adverb describe another adverb? Thank you in advance for your help.