The Multi-Regional Storage Class is the optimal choice for meeting the requirement of high availability and resilience across regions. It replicates data across multiple regions, ensuring high durability and availability, even in the face of regional failures. This makes it ideal for storing critical data that demands high availability and disaster recovery capabilities.

Other storage classes like Nearline, Standard, Dual-Regional, and Regional are tailored for specific use cases and do not offer the same level of redundancy and availability necessary for highly confidential documents. By opting for Multi-Regional Storage, your company can guarantee that the data remains accessible and resilient, regardless of regional outages.