What type of insurer must adhere to specific state regulations?

The correct choice is an admitted insurer, as this type of insurer is required to comply with specific regulations set forth by state insurance authorities. Admitted insurers are those that have obtained a license from the state to conduct insurance business and are therefore subjected to the state's legal and regulatory framework, including filing rates and forms for approval and maintaining certain reserves.

In contrast, captive insurers, which are typically formed by a parent company to insure its own risks, may not be subject to the same level of state regulation. Eligible surplus lines insurers are those that can provide coverage for risks that admitted insurers are unwilling to insure, and while they have some regulatory requirements, they generally operate under a different set of rules. Nonadmitted insurers, which are unauthorized to conduct business in a state, also have fewer regulatory obligations. Therefore, it is the admitted insurer that must adhere to specific state regulations, ensuring consumer protection and policy accountability.