Which storage solution should a solutions architect recommend for use after the migration?

Explanations:

AWS DataSync is used for transferring data between on-premises storage and AWS but does not provide an NFS interface for persistent storage. It is not suitable for direct application data storage as required.

Amazon Elastic Block Store (EBS) provides block-level storage and does not support NFS. It is ideal for applications requiring high-performance block storage but cannot be used directly with NFS by the legacy application.

Amazon Elastic File System (EFS) provides a fully managed, scalable, and NFS-compatible file storage service that can be mounted directly by the legacy application. This makes it the ideal solution for migrating the application while maintaining its existing communication protocol.

Amazon EMR File System (EMRFS) is specific to Amazon EMR for processing large data sets and is not a standalone file storage service that supports NFS for general application use. It is not suitable for the legacy application’s storage requirements.