Final answer:
An ABN form needs to be signed by patients who have Medicare insurance before any service or procedure is performed.
Step-by-step explanation:
The correct answer is option 3) Medicare; before any service or procedure is performed. An ABN form, or Advanced Beneficiary Notice, needs to be signed by patients who have Medicare insurance before any service or procedure is performed. This form serves as a notification to the patient that the service or procedure may not be covered by Medicare, and that the patient will be responsible for the cost if Medicare denies payment.