What is the theological significance of Onesimus' transformation from a runaway slave to a beloved brother in Christ, as highlighted in Paul's letter to Philemon?

A It reinforces the social hierarchies and economic structures of the Roman Empire. B It demonstrates the power of the church to enforce strict disciplinary measures against wrongdoers. C It exemplifies the transformative power of the Gospel to dismantle social barriers and promote reconciliation and equality in Christ. D It proves that all slaves are inherently untrustworthy and prone to rebellion.