Final answer:
CPT code 99215 is used for an established patient's office visit that includes a comprehensive history, comprehensive exam, and high medical decision-making with a moderate to high presenting problem, averaging 40 minutes.
Step-by-step explanation:
The code that should be used for an Established Patient with a Comprehensive history, Comprehensive exam, and High medical decision-making with a presenting problem that is moderate to high, and the service averages 40 minutes, is B) 99215. This code is part of the Current Procedural Terminology (CPT) codes used in the medical field for billing purposes. The described scenario fits the requirements for CPT code 99215, which is used for office or other outpatient visits for the evaluation and management of an established patient.