How does the Apostle Paul's appeal to 'adoption as sons' (Galatians 4:5) challenge the social norms of the Roman Empire?

A It reinforced the existing Roman laws regarding familial inheritance. B It emphasized the biological lineage of believers within the Christian community. C It offered a spiritual status available to all believers, regardless of social standing or ethnicity, contrasting with the Roman system where adoption primarily benefited wealthy families seeking heirs. D It was a direct endorsement of the Roman practice of selling children into slavery.