This solution meets the requirements most cost-effectively because it enables the company to migrate its on-premises NFS data store to AWS without changing the existing applications or workflows. AWS Storage Gateway is a hybrid cloud storage service that provides seamless and secure integration between on-premises and AWS storage. Amazon S3 File Gateway is a type of AWS Storage Gateway that provides a file interface to Amazon S3, with local caching for low-latency access. By setting up an Amazon S3 File Gateway, the company can store and retrieve files as objects in Amazon S3 using standard file protocols such as NFS. The company can also use an Amazon S3 Lifecycle policy to automatically transition the data to the appropriate storage class based on the frequency of access and the cost of storage. For example, the company can use S3 Standard for frequently accessed data, S3 Standard-Infrequent Access (S3 Standard-IA) or S3 One Zone-Infrequent Access (S3 One Zone-IA) for less frequently accessed data, and S3 Glacier or S3 Glacier Deep Archive for long-term archival data.

Option A is not a valid solution because AWS Storage Gateway Volume Gateway is a type of AWS Storage Gateway that provides a block interface to Amazon S3, with local caching for low-latency access. Volume Gateway is not suitable for migrating an NFS data store, as it requires attaching the volumes to EC2 instances or on-premises servers using the iSCSI protocol. Option C is not a valid solution because Amazon Elastic File System (Amazon EFS) is a fully managed elastic NFS file system that is designed for workloads that require high availability, scalability, and performance. Amazon EFS Standard-Infrequent Access (Standard-IA) is a storage class within Amazon EFS that is optimized for infrequently accessed files, with a lower price per GB and a higher price per access. Using Amazon EFS Standard-IA for migrating an NFS data store would not be cost-effective, as it would incur higher access charges and require additional configuration to enable lifecycle management. Option D is not a valid solution because Amazon EFS One Zone-Infrequent Access (One Zone-IA) is a storage class within Amazon EFS that isoptimized for infrequently accessed files that do not require the availability and durability of Amazon EFS Standard or Standard-IA. Amazon EFS One Zone-IA stores data in a single Availability Zone, which reduces the cost by 47% compared to Amazon EFS Standard-IA, but also increases the risk of data loss in the event of an Availability Zone failure. Using Amazon EFS One Zone-IA for migrating an NFS data store would not be cost-effective, as it would incur higher access charges and require additional configuration to enable lifecycle management. It would also compromise the availability and durability of the data.