Final answer:
An adverb modifies or describes a verb, adjective, or adverb. 'Well' is an example of an adverb.
Step-by-step explanation:
An adverb is a word that modifies or describes a verb, adjective, or other adverb. It provides information about how, when, where, or to what extent something is done. In the given options, the only word that functions as an adverb is well. For example, in the sentence 'She sings well,' the adverb 'well' describes how she sings.
Learn more about Adverbs