What is the accounting measurement of an insurance company's future obligations to its policyowners?

The correct choice is reserves, which represents the accounting measurement of an insurance company's future obligations to its policyholders. Reserves are critical in the insurance industry as they are funds set aside to pay future claims. Insurance companies are required to maintain adequate reserves to ensure they can meet the liabilities arising from policies they have underwritten. This is essential for the financial stability and regulatory compliance of the company.

Reserves are calculated based on various factors, including the expected frequency and severity of claims, the duration of coverage, and demographic factors relating to the insured population. Having proper reserves allows the insurance company to manage its obligations effectively and ensures policyholders are protected against losses.

In contrast, credits may refer to premiums or adjustments but do not directly relate to obligations. A surplus account typically refers to excess assets over liabilities and reflects the company's financial health rather than a direct obligation to policyholders. Lastly, a retention fund often pertains to self-insured retentions or amounts that a company keeps for its own risks, rather than obligations to policyholders. Thus, reserves are the most relevant and accurate term for indicating an insurer's future obligations.