Complete verbs consist of two parts:
* Main verb: The action or state of being (e.g., hear, run, sleep)
* Helping verb: A verb that helps the main verb express tense, mood, or voice (e.g., have, has, had, will, would).
In "had heard,"
* "heard" is the main verb.
* "had" is the helping verb that indicates the past perfect tense.
Therefore, "had heard" is a verb phrase, not a complete verb. It needs a subject to be a complete sentence (e.g., "She had heard the news.").