In the story of Mephibosheth (2 Samuel 9), what does David's treatment of Jonathan's disabled son reveal about the nature of covenant loyalty in the Old Testament?

A It primarily demonstrates the importance of physical strength and ability in leadership. B It illustrates the limited scope of royal generosity, extending only to those who can provide a benefit. C It reflects a cultural practice of eliminating potential threats to the throne. D It exemplifies the enduring nature of covenant commitments, extending beyond personal advantage and even to future generations, demonstrating grace and compassion.