Considering the context of the divided kingdom, what was the primary theological message conveyed through the prophet Amos's condemnation of social injustice in Israel?

A That God only cares about ritualistic sacrifices and offerings. B That God's covenant with Israel was unconditional and unbreakable. C That true worship of God requires ethical living and justice for the oppressed, and neglecting these principles would lead to divine judgment, regardless of religious practices. D That the Northern Kingdom was superior to the Southern Kingdom in its religious practices.