Answer: The combined sentence uses a compound verb.
Step-by-step explanation: A compound verb is a verb formed with more than one word. Two types of compound verbs are phrasal verbs and prepositional verbs. In the combined sentence, "were off" is a compound verb. Moreover, "were off" is the conjugated form of the phrasal verb "go off", which means "to leave" or "to go away". Therefore, the correct answer is compound verb: the combined sentence does not include a compound subject, nor does it use a compound object.