The correct option is Enable S3 cross-Region replication (CRR) between buckets in different AWS Regions. This approach provides automatic, managed replication across Regions and satisfies the requirement to retain at least two copies of data in geographically distant locations.

S3 cross-Region replication or S3 CRR runs inside Amazon S3 and replicates objects asynchronously after they are created or updated. It integrates with S3 versioning and replication rules so you avoid building and maintaining custom copy logic or compute resources, which reduces operational overhead and overall cost compared with self managed solutions.

AWS DataSync is intended for efficient transfers and migrations and it requires configuring tasks and agents. It is not the native mechanism for continuous object level replication between S3 buckets and so it is less suited for this regulatory requirement.

S3 same-Region replication (SRR) replicates objects only within the same AWS Region and therefore does not meet the rule that copies must be in Regions hundreds of miles apart.

Run a nightly job on an Amazon EC2 instance to copy objects to a bucket in another Region can work but it is operationally inefficient. Managing instances, scripts, schedules and error handling increases cost and failure surface compared with using S3 CRR.

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