Final answer:
A UPS delivery area would best be described as a functional region because its boundaries are defined by the limits of the delivery services provided by UPS.
Step-by-step explanation:
A UPS delivery area would best be described as a functional region. Functional regions are defined by a practical function within a given area and their boundaries are associated with the limits of the services provided. In the case of UPS, the delivery area is the region within which UPS offers delivery services, and the border of this area is determined by the outermost points that UPS is willing to service. These boundaries can change based on the company's operations and service decisions, making it a perfect example of a functional region as opposed to a formal region with fixed official boundaries, or a perceptual region defined by people's feelings or attitudes.