Final answer:
A TRICARE beneficiary is typically responsible for paying 20% of covered inpatient and outpatient services, after deductibles have been met.
Step-by-step explanation:
The percentage a TRICARE beneficiary must pay for covered inpatient and outpatient services (other than the annual deductible or disallowed amounts), often referred to as the co-insurance payment, is typically 20%. This means that after paying deductibles, a TRICARE beneficiary would be responsible for paying 20% of the covered health care costs, while TRICARE pays the remaining 80%. This cost-sharing arrangement helps manage the health care spending by involving the beneficiary in the payment process, which can lead to more conscientious use of medical services. Given the information provided, the correct answer is a) 20%.