In which of the following sentences is the underlined word a possessive pronoun

I'm not sure, because you didn't provide any of the sentences. A possessive pronoun takes the place of saying a person or thing owns something. For example, we could say "This backpack is Max's." If we were to rewrite this sentence using a possessive pronoun, we woud say, "This backpack is his." The word "his" would be the possessive pronoun because it indicates ownership and takes the place of "Max's". Other examples of possessive pronouns include: hers, thiers, ours, mine, yours, whose, and its.