A company runs an application on premises.

The correct answer is D because the company needs shared storage for Amazon EC2 instances that are deployed across multiple Availability Zones , and the application already relies on Linux file system permissions without requiring application code changes. Amazon EFS is a fully managed, elastic, shared file system that supports the NFS protocol , which is commonly used by Linux-based applications. It can be mounted concurrently from multiple EC2 instances across multiple Availability Zones, making it the best fit for this requirement.

Amazon EFS preserves standard file system semantics and POSIX-style permissions, which means the company can continue using familiar Linux file permissions and ownership models. This allows the application to work without code modification. EFS is also highly available and durable because it is designed as a Regional service that stores data redundantly across Availability Zones.

Option A is incorrect because Amazon S3 is object storage, not a native shared POSIX file system. Mounting S3 does not provide the same file system behavior and permissions model required by the application. Option B is incorrect because instance store volumes are ephemeral and tied to individual EC2 instances, so they are not suitable for shared, durable storage across multiple instances. Option C is incorrect because Amazon EBS volumes are block storage volumes that are generally attached to a single instance and are not the best solution for shared multi-AZ file access.

AWS best practices recommend Amazon EFS when Linux applications require a shared file system, file permissions, and multi-instance access with minimal operational changes. Therefore, Amazon EFS is the most appropriate solution.