Them is the correct choice of pronoun-antecedent agreement to maintain consistency in plural reference, as "the musicians" refers to all musicians involved. "Them" denotes the group of musicians, following the conventions of Standard English.

The appropriate pronoun-antecedent agreement is "they," as it refers to both Michael and Jennifer who are working together. Using "they" maintains consistent plural reference and aligns with the conventions of Standard English.

The correct choice of pronoun-antecedent agreement is "hers" because the context implies that the book either belongs to Sarah or Natalie, and both are female. Using "hers" maintains a consistent singular reference and aligns with the conventions of Standard English.

Here, the correct choice of pronoun-antecedent agreement is "his or her" because "each musician" is a singular reference. The pronoun "his or her" indicates that the musicians can be either male or female and maintains a consistent singular reference, which follows the conventions of Standard English.

In this case, "he" is the appropriate pronoun-antecedent agreement because Juan is a singular noun referring to a specific person. Using "he" maintains a consistent singular reference and aligns with the conventions of Standard English.