Final answer:
Commands, agencies, and headquarters involved in military operations and joint operations are overseen by the U.S. armed forces, including the Army, Navy, Marine Corps, and Air Force.
Step-by-step explanation:
The subject of this question is: Social Studies
Commands, agencies, and headquarters involved in training, preparation, deployment, support, sustainment, redeployment, and demobilization or committed to a joint operation are part of the military's organizational structure. These elements are overseen by the U.S. armed forces, which include the Army, Navy, Marine Corps, and Air Force.
For example, the Department of Defense, National Security Council, and Joint Chiefs of Staff are some of the key components in this organizational structure. They play a crucial role in planning and coordinating military operations.