Final answer:
The Chairman of the Joint Chiefs of Staff and the Combatant Command must maintain Unity of command to ensure effective military operations and a cohesive effort towards achieving military objectives.
Step-by-step explanation:
The Chairman of the Joint Chiefs of Staff and the Combatant Command must maintain C) Unity of command. This principle is crucial for effective military operations. Unity of command ensures that all forces are under one single commander who has the requisite authority to direct and coordinate the actions of all military resources. This prevents confusion and conflict of orders, allowing for a cohesive and united effort towards the achievement of the assigned military objectives. The chairman serves as the principal military advisor to the president and is charged with overseeing the interests of the U.S. in terms of national security and strategic planning. Operational independence, as suggested by the term, implies carrying out operations without undue political influence, while maintaining allegiance to the chain of command and national objectives.