Which part of speech describes an action in various tenses?

The correct choice is that a verb describes an action in various tenses. Verbs are essential components of sentences that indicate what the subject is doing or what is happening. They can change form to reflect different times, such as past, present, and future, which allows them to express actions that occur at various moments. For example, the verb "run" can change to "running" for the present continuous tense, "ran" for the past tense, or "will run" for the future tense. This flexibility in form and function is what makes verbs a critical part of speech for conveying action and time in language.