Final answer:
The medical office is using the Open hours scheduling method when patients who arrive without appointments are seen in the order of their arrival.
Step-by-step explanation:
When patients arrive without appointments and are generally seen in the order of their arrival, the medical office is using the Open hours scheduling method. This type of scheduling is also often referred to as walk-in hours or first-come, first-served scheduling. It contrasts with other methods such as Double booking, where two patients are scheduled at the same time slot; the Wave scheduling, where multiple patients are scheduled at the top of the hour followed by shorter appointments throughout the hour; and Walk-in hours, which can sometimes be a common term for open hours but is more often used for clinics that do not operate on scheduled appointments at all.