Here is a sentence:
I can barely see a foot in front of me in this fog.
As a standalone sentence, it can't be the answer to the question starting with "What can you..." since "a foot" here is a unit of the length of vision, and so the question it may be the answer to might be "How far can you see in this fog?" Would I be right saying that "barely" in this sentence modifies "can" whereas "a foot" modifies "to see"? If yes, does it mean that it plays the role of an adverb? But can a noun be an adverb? If yes, what type of adverb it is in the above sentence?
P.S. There's a related post on the role of "a foot" in a sentence, but it doesn't seem to meet with my request.