Well, if we know that an adverb is a modifier of verb's or word groups such as a circumstance, a time, or a place then looking at this question would be more understandable.
In this case, examine your options.
A) is a noun. --> noun is a person place or thing-->e.g friends.
B) is unfitting to the question being asked I should think.
C) is something like what we are looking for. It is a verb, it is an action. An adverb modifies an action.
Does this make sense?