Final answer:
The unique service characteristic that deals specifically with the inability to inventory services is Perishability.
Step-by-step explanation:
The unique service characteristic that deals specifically with the inability to inventory services is D. Perishability.
In the context of services, perishability refers to the fact that services cannot be stored or saved for future use. Unlike physical products, services are consumed as they are provided, and they cannot be stored or sold at a later time.
For example, if a doctor has an empty appointment slot in their schedule and no patient shows up, that time cannot be saved or used for another patient once the time has passed.