Final answer:
The primary reasons for designating a Deputy IC are to provide leadership support, ensure continuity of operations, and facilitate the delegation of authority in complex or large-scale incidents.
Step-by-step explanation:
The primary reasons to designate a Deputy Incident Commander (Deputy IC) are to enhance incident management by providing leadership support, ensuring continuity of operations, and facilitating the delegation of authority. A Deputy IC may be necessary when the incident is complex or spans across multiple jurisdictions, thus requiring shared authority among agencies or when the primary Incident Commander (IC) is not able to be present or needs to focus on other critical aspects of the incident. Furthermore, it helps in preventing a single point of failure in incident command, which is essential during large-scale events where decisions must be made quickly and effectively.