How does the story of Mephibosheth, Jonathan's son who was crippled, illustrate David's understanding of covenant theology and his relationship with Saul's family (2 Samuel 9)?

A David sought to eliminate any potential heirs to Saul's throne, ensuring his own dynasty's security. B David showed kindness to Mephibosheth solely out of political strategy to gain favor with Saul's former supporters. C David's treatment of Mephibosheth was an act of simple charity, unrelated to any deeper commitments. D David's actions were rooted in his covenant with Jonathan, demonstrating loyalty and fulfilling his promise to show kindness to Jonathan's descendants.