Final answer:
The insurance provider is generally responsible for assessing claims and determining eligibility for reimbursement under a policy agreement.
Step-by-step explanation:
The entity responsible for determining whether all or part of a claim is eligible for reimbursement is typically D) The insurance provider. The insurance company assesses claims based on the policy agreement with the claimant. They review the circumstances of the claim, verify coverage, and determine the extent of their obligation to pay for the losses or services claimed.
The claimant is responsible for submitting the claim, the tribunal or court may become involved in the event of a dispute, the registrar may handle administrative tasks, and the healthcare professional provides the services but does not decide on reimbursement eligibility.