Final answer:
The sentence with incorrect pronoun antecedent agreement is 'Everyone has an opinion.' It should be either 'Everyone has opinions' or 'People have their own opinions.'
Step-by-step explanation:
The sentence with an incorrect shift in pronoun antecedent agreement is "Everyone has an opinion." To correct this, one should remove the pronoun to simply state, "Everyone has opinions," or make the antecedent plural as in, "People have their own opinions." Pronouns must agree in number with the nouns they refer to, which are called antecedents. In this case, 'everyone' is considered a singular indefinite pronoun, so it should not be followed by 'there,' which is a plural possessive pronoun unless the context of the conversation has already established 'everyone' as a group made up of known individuals.