Who is the Secretary of the Navy?

The Secretary of the Navy is a key official responsible for the oversight and administration of the Navy and Marine Corps. The correct answer, Thomas Harker, serves in this vital role, which encompasses a range of responsibilities including the formulation of policies, management of resources, and ensuring the readiness of naval forces. As a civilian leader within the Department of Defense, the Secretary also plays a crucial role in advising the President and coordinating with other branches of the military.

The other individuals mentioned hold significant positions but do not occupy the role of Secretary of the Navy. For instance, Captain Castro and Command Master Chief McDermott may hold leadership roles in the Navy but are not in the Secretary's position. Rear Admiral Bruce L. Gillingham, while an important figure as the Chief of Naval Personnel, does not serve as the Secretary either. Thus, identifying Thomas Harker as the Secretary of the Navy is correct based on his responsibilities and the current structure of naval leadership.