A company needs a backup strategy for Amazon EC2 data and several Amazon S3 buckets. Regulatory requirements mandate that backups be retained for a specific retention period and must not be altered during that period. Which solution meets these requirements?

The correct solution is to use AWS Backup with a backup vault that has a vault lock in compliance mode. Compliance mode ensures that backups cannot be deleted or altered by any user, including the root account, for the duration of the retention period, satisfying the regulatory requirement for immutability. AWS Backup also supports backing up both EC2 instances and S3 buckets. Using a vault lock in governance mode allows authorized users to make changes to the lock settings, which violates the immutability requirement. Amazon Data Lifecycle Manager is primarily for managing EBS snapshots and does not directly manage S3 backups or offer immutable retention for S3. Amazon S3 File Gateway is for hybrid cloud storage and does not inherently provide immutable backups across EC2 and S3 with regulatory compliance.