Answer:
The correct answer would be option A, When the incident scope is complex or beyond existing authorities.
Step-by-step explanation:
Delegation of authority means passing the power to the level where it is required or practiced better than the existing holders of the authority.
So according to this question, delegation of authority is needed where the incident scope is complex, which means that this could not be understood by the current or existing authorities clearly, or the incident scope is beyond the existing authorities which means the incident scope does not come within the power range of the authorities. So in such scenarios, the best solution is to delegate authority to those who are within the scope of the incident and also they understand it pretty well.