The book of Philemon addresses a specific situation. What is the central theme or request that Paul makes of Philemon in his letter regarding Onesimus?

A Paul asks Philemon to financially support Paul's missionary journeys. B Paul instructs Philemon to publicly rebuke Onesimus for his past transgressions as a warning to other slaves. C Paul urges Philemon to grant Onesimus his freedom and receive him back as a brother in Christ, not merely as a slave. D Paul commands Philemon to sell Onesimus and donate the proceeds to the church in Colossae.