The sentence that has a pronoun-antecedent disagreement error is "Each journalist has to decide what beat they want to cover." Option A.
Since "journalist" the antecedent is singular and the pronoun "their" is in the plural form, the pronoun disagrees with the antecedent, so that, there is a pronoun-antecedent agreement error in the sentence. The way to correct the mistake is either by becoming both the pronoun and antecedent singular or plural.
