Which part of speech can describe how, when, or where an action occurs?

The correct answer is an adverb because adverbs modify verbs, adjectives, or other adverbs and provide additional details about the action. They specify how, when, or where something happens. For example, in the sentence "She runs quickly," the adverb "quickly" describes how she runs. Similarly, in the sentence "He arrived yesterday," "yesterday" indicates when the action took place. An adverb enhances the meaning of a verb by providing this contextual information.

Nouns refer to people, places, things, or ideas, and do not provide details about actions. Pronouns substitute for nouns and also do not convey information about the manner, time, or location of actions. Conjunctions connect words, phrases, or clauses, but they do not describe actions or provide adverbial information regarding how, when, or where something occurs. Thus, the ability of adverbs to modify actions with specific context makes them the correct choice in this case.