ANSWER:
The correct answer is C)Predicate nominative
STEP-BY-STEP EXPLANATION:
A predicate nominative (also called a predicate noun) is a word or group of words that completes a linking verb and renames the subject. A predicate nominative is always a noun or a pronoun.
THEIRS is used as a possessive pronoun, being a possessive form of they. It can refer to a singular or plural noun, and it can be the subject, object, or complement of a verb or the object of a preposition
