Answer: C) Past participle.
Step-by-step explanation: the past participle of a verb usually expresses an action that has been completed, it is used like an adjective or like a verb in the formation of compound verbs in past. In the given sentence the word "held" could represent just a past form of "hold" but as it is right after the verb "have" we know it is a past participle, used to form the conjugaison "have held" so the answer is option C.