How does the Apostle Paul, in his letter to Philemon, subtly challenge the social norms and legal structures of the Roman Empire regarding slavery?

A By explicitly condemning slavery as inherently evil and demanding its immediate abolition throughout the empire. B By using persuasive language and appealing to Philemon's Christian faith to encourage him to receive Onesimus, a runaway slave, not as property but as a brother in Christ, thereby undermining the master-slave dynamic. C By threatening Philemon with divine punishment if he does not immediately free all his slaves, thus wielding his apostolic authority to enforce social change. D By advocating for a gradual and legal process of emancipation, working within the existing Roman legal framework to improve the conditions of slaves.