Final answer:
The premium amount must be included on the first page of a Medicare supplement policy, stating the insurer's right to change premium amounts.
Step-by-step explanation:
The provision that must be included on the first page of a Medicare supplement policy, which states the insurer's right to change premium amounts, is the premium amount. This information is important for policyholders to be aware of any potential changes in their premiums. It allows them to have a clear understanding of the cost of their coverage and to make informed decisions.