Which part of speech tells something about the subject or indicates an action?

The correct answer is a verb because a verb is a crucial part of speech that expresses an action, occurrence, or state of being related to the subject of a sentence. Verbs can describe actions like "run," "sing," or "dance," and can also indicate states of being with forms of "to be," such as "is," "are," and "was." By doing so, verbs help convey what the subject is doing or experiencing, making them essential to complete thoughts in sentences.

In contrast, nouns identify people, places, things, or ideas; adjectives describe or modify nouns; and adverbs modify verbs, adjectives, or other adverbs to provide additional detail about how, when, where, or to what extent something happens. Therefore, while these other parts of speech play important roles in sentence structure, it is the verb that specifically tells about the action or state involving the subject.