Which of the following is a word or word group that expresses action or a state of being?

A verb is a word or word group that indicates an action (such as "run," "swim," or "dance") or a state of being (such as "is," "are," or "exist"). In the English language, verbs are essential components of sentences as they provide information about what the subject is doing or the condition of the subject. This action or state of being is crucial for conveying meaning and structure in communication.

In contrast, a pronoun replaces nouns in a sentence and does not express action or a state of being. A noun identifies a person, place, thing, or idea, while an adjective describes or modifies a noun, providing additional information about it, such as its qualities or characteristics. Therefore, the defining feature of a verb as expressing action or a state of being makes it the correct answer to the question.