The correct answer is D) The Operational Control Authority. Under Naval Control of Shipping, the Operational Control Authority is responsible for routing and diverting ships and convoys. This is because the Operational Control Authority has the overall command and control of naval forces, including the authority to direct the movement and actions of ships and convoys as needed for military operations or security reasons. The other options are incorrect because the National Shipping Authority is responsible for overall management of merchant shipping, the Maritime Defense Zone Sector is a regional command, and any Navy Command would not have the specific authority for routing and diverting ships under Naval Control of Shipping protocols.