Which of these is a requirement of ARFF regarding staffing?

The requirement regarding staffing in the context of Aircraft Rescue and Firefighting (ARFF) recognizes that smaller airports may benefit from a centralized staffing approach. This means that at smaller airports, it can be advantageous to consolidate ARFF operations rather than maintaining fully separate teams for each function. This centralization can lead to more efficient use of limited resources, ensuring that ARFF units can respond effectively without duplicating efforts or staffing levels that may not be justified given the airport's size and traffic volume.

This approach takes into account the unique operational demands and available resources of smaller airports, suggesting a flexible staffing model tailored to the specific circumstances of each airport rather than a one-size-fits-all solution.

The other options do not align with the principles outlined by regulatory frameworks such as those set by the FAA, which emphasize the importance of adequate staffing based on specific airport characteristics and needs.