What is an adverb?

An adverb is a word that modifies a verb, an adjective, or another adverb, providing additional information about how, when, where, or to what extent something happens. For example, in the sentence "She runs quickly," the word "quickly" modifies the verb "runs" by describing the manner in which she runs. Adverbs can also modify adjectives, as in "He is very tall," where "very" enhances the adjective "tall." Additionally, adverbs can modify other adverbs, such as in "She runs quite fast," where "quite" modifies the adverb "fast." This versatility in modifying various parts of speech is what distinctly characterizes adverbs, solidifying choice C as the correct understanding of what an adverb is.