The organization that has line authority to oversee the management of multiple incidents being handled by separate Incident Command organizations would be D. Area Command.
The Area Command usually comes in during multiple incidents or when incidents become too much to handle for the local units or of the Incident Command organizations assigned to them. What happens is that they become the established commander of the area and provide full support to the completion of the incidents being responded to. They see to it they everything is completed, in order, and a success.
