Object storage is the correct answer because it is designed for storing large amounts of unstructured data. It is highly durable and available, and it's generally more cost-effective for archival purposes where data is not frequently accessed, making it ideal for long-term storage of compliance data. Block storage is typically used for databases and high-performance workloads where data needs to be accessed and modified at a block level, which is not necessary for archival purposes and is more expensive for this use case. File storage, such as NAS, is great for shared data access but usually comes with a higher cost than object storage and is more suited to active file sharing rather than archival storage. SAN provides high performance and reliability but is typically overkill and too costly for archival purposes.