Option D is the right answer
An Incident Commander's scope of authority is derived from existing laws, agency policies, procedures, and/or through a delegation of authority from the agency administrator or elected official.
Within his/her scope of authority, the Incident Commander establishes incident objectives, then determines strategies, resources, and ICS structure based on the incident objectives.
The incident commander is the person responsible for all aspects of an emergency response; including quickly developing incident objectives, managing all incident operations, application of resources as well as responsibility for all persons involved.
The role of incident commander may be assumed by senior or higher qualified officers upon their arrival or as the situation dictates. Even if subordinate positions are not assigned, the incident commander position will always be designated or assumed.