Final answer:
The methodology used for critical care services that results in composite APCs is Conditionally Comprehensive. It involves bundling services into a single payment but allows for unbundling under certain conditions.
Step-by-step explanation:
The methodology used for critical care services, imaging, and mental health services that results in composite Ambulatory Payment Classifications (APCs) is Conditionally Comprehensive. Under this methodology, certain services are packaged into a single payment rate rather than being paid for individually, which encourages hospitals to provide care in the most cost-effective manner possible. However, the bundling is 'conditional,' meaning that if certain conditions are not met, services may still be billed separately.