Answer :
If you are a member of the US Navy, your organization is part of the Department of Defence. The US Department of Defense is made up of Army, Marine Corp, Navy, Airforce, the Unified Combatant Command, US element of multinational command, Defence Intelligence Agency and National Security Agency.
The correct answer is D.
The United States Navy is a branch of the Armed Forces of the United States that depends administratively on the Department of the Navy and is a division of the Department of Defense headed by the Secretary of Defense. Its main function is to maintain, train and equip naval forces for combat and maintain the freedom in the seas.