In the sentence "They knew all of the answers because they studied," what is "studied" classified as?

In the sentence "They knew all of the answers because they studied," the word "studied" functions as a verb. It indicates the action that the subject (they) performed in order to achieve a particular outcome (knowing the answers). Verbs are words that express actions, occurrences, or states of being, and in this context, "studied" clearly conveys the action taken by the subjects.

The other options, such as adverb, noun, and adjective, do not accurately describe the role of "studied" in this sentence. An adverb modifies verbs, adjectives, or other adverbs, but "studied" is not being modified here; it is the main action. A noun represents a person, place, thing, or idea, which does not fit since "studied" does not name anything. Lastly, an adjective describes or modifies a noun, but "studied" is not serving this purpose in the sentence. Thus, the classification of "studied" as a verb is the correct choice.