In this problem, the word POPULER would be C. predicate adjective.
It can't be an indirect object since it isn't even an object to begin with. As for objective complement, it might have been considered to be one if the verb used isn't a linking verb. Since the verb used is a linking verb, then it isn't considered to be an objective complement. It isn't a predicate nominative because the word following after the linking verb is an adjective, not a noun or a pronoun. So the only answer left would be C. predicate adjective.
