C because of the apostrophe after the s which indicated that they both participated
The possessive pronouns that can be used as predicate nouns are the following: mine, ours, yours, hers, theirs and his. Possessive pronouns are pronouns that show possession or ownership. These can be classified into two according to how it is used in the sentence: as a subject or as a predicate.
The neighbor has to be the antagonist, because the protagonist loved his dog very much and his neighbor killed his dog, the protagonist even called his neighbor evil, so I would go with C, the neighbor.
