Final Answer:
The type of incident that is the most complex, requiring national resources to safely and effectively manage and operate is a Type 1 incident.
Step-by-step explanation:
A Type 1 incident is the most severe and complex level of incident as classified by the Incident Command System (ICS). It requires extensive national resources, coordination, and management due to its scale, impact, and complexity. Type 1 incidents often involve significant threats to life, property, and the environment, requiring a coordinated response from multiple agencies and jurisdictions.
In the ICS, incidents are categorized into five types (Type 1 to Type 5), with Type 1 being the most severe. These classifications help emergency responders and agencies allocate resources and manage incidents effectively based on their complexity and magnitude.