The correct choice is Amazon EFS. Amazon EFS provides a fully managed elastic Network File System that multiple EC2 instances can mount concurrently across multiple Availability Zones in the same Region so instances can read update and collaborate on the same files.

Amazon EFS is POSIX compliant and supports concurrent access from many EC2 instances while it automatically scales storage and throughput as needed. This makes it well suited for shared file based workloads that require low administrative overhead and multi AZ availability.

Amazon S3 is object storage and not a POSIX compliant file system so it cannot be mounted like NFS for simultaneous file sharing across instances. Amazon S3 is ideal for object storage and data lakes but not for POSIX file sharing.

Amazon EBS provides block storage that is normally attached to a single instance and while some volume types offer Multi Attach it is limited to the same Availability Zone. Amazon EBS does not provide a managed multi AZ shared file system.

EC2 Instance Store is ephemeral storage that is physically attached to the host and it cannot be shared between instances. EC2 Instance Store also loses data when the instance stops or terminates so it is unsuitable for centralized shared file storage.

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