Final answer:
You can return a Medicare Supplement policy for a 100% refund within a 30-day free-look period after policy delivery.
Step-by-step explanation:
A Medicare Supplement policy, also known as Medigap, can be returned within a specific time frame after policy delivery for a 100% refund. This time frame is referred to as the "free-look" period. The correct answer to how many days a policyholder has to return a Medicare Supplement policy for a full refund is d. 30 days. During this period, the policyholder can decide if they want to keep the insurance or not without any financial penalty. It's a consumer protection feature that allows the policyholder to fully review the policy.