The transition to managed care health plans in the 1980s and 1990s is significant because

a. many of the legal principles of managed care have been found to violate the Age Discrimination in Employment Act (ADEA)

b. the transition has been short-lived, and since the 2000s there has been a transition back to fee-for-service plans

c. both private, employer-provided health plans and public plans (Medicare) embraced the transition from fee-for-service plans

d. it removed many systemic inefficiencies but has not prevented healthcare costs from increasing at rates greater than general inflation rates