Answer:
The 4th sentence has helping verb, "had".
Step-by-step explanation:
A linking verb connects the subject of the sentence to a noun/pronoun/adjective. A helping verb helps the main verb tell about an action or make a statement. You can tell the difference because linking verbs do not show actions. For example, the sentence "Johnny was a student" shows no action, so "was" is a linking verb. The sentence "Johnny is doing a test" shows that Johnny is doing an action (completing his test), making "is" a helping verb.