The correct answer isCbecause the existing application usesNFS storagefor an image cache that isa few terabytes in size, and the company wants themost cost-effective cloud alternative.Amazon EFS One Zoneis a managed file storage service that supports theNFS protocol, which allows the application to continue using a familiar file-based interface with minimal architectural change. Because this is acache, not primary durable data, storing it in aOne Zonefile system is a cost-optimized choice compared with a Regional EFS deployment.

Amazon EFS is designed for shared file storage and can scale to multiple terabytes automatically. It avoids the operational overhead of managing EC2 instances and local disks for cache storage. It is also better aligned than object storage for workloads that already expect direct NFS semantics. The application can mount the EFS file system and use it as the cache backend without redesigning around object APIs or in-memory caching models.

Option A is incorrect becauseElastiCache Memcachedis an in-memory cache and is typically much more expensive for multi-terabyte cache data than file storage. Option B is incorrect because using EC2 instance store volumes creates significant management overhead and the cache would be lost whenever instances are terminated or replaced. Option D is incorrect becauseAmazon S3 Express One Zoneis object storage, not NFS storage, and would require application redesign and additional metadata management in DynamoDB.

AWS storage guidance recommends matching file-based workloads to managed file services. For a largeNFS-based cache,Amazon EFS One Zoneis the most cost-effective and operationally simple solution.