Final answer:
Most states require insurers to file policy forms with the state's Department of Insurance.
Step-by-step explanation:
The majority of states require insurers to file policy forms with Option 4: The state's Department of Insurance. The U.S. insurance industry is primarily regulated at the state level, and each state has its own Department of Insurance that oversees insurance activities within their jurisdiction. The state insurance regulators play a crucial role in ensuring that insurance policies meet the necessary requirements and comply with state laws.