Which part of speech tells you how an action is performed?

The correct choice is adverb because adverbs modify verbs, adjectives, or other adverbs by providing more information about how an action is performed. They often answer questions like "how?", "when?", "where?", "why?", and to what extent. For example, in the sentence "She runs quickly," the word "quickly" is an adverb that tells us how she runs. This function of describing the manner or degree of an action distinctly categorizes adverbs as key parts of speech for expressing actions.

Adjectives primarily modify nouns, providing details about a person, place, thing, or idea, rather than the action itself. Prepositions are used to show relationships between nouns (or pronouns) and other words in a sentence, often indicating location or direction. Interjections express strong emotion or surprise and are not related to the action of the verb but rather convey feelings or reactions independently. Thus, the adverb is the only option that directly pertains to describing the manner of an action.