In the book of Philemon, what is the underlying theological significance of Paul's appeal regarding Onesimus?

A Paul is simply asking Philemon to forgive Onesimus for running away. B Paul is subtly demanding Philemon free Onesimus immediately. C Paul is demonstrating the transformative power of the Gospel in reconciling former enemies as equals in Christ, challenging the social hierarchies of slavery. D Paul is primarily concerned with maintaining social order and upholding the institution of slavery.