The correct answer is A. NFS (Network File System).

NFS is a file-level storage protocol, which means it allows clients to access shared storage as if it were part of their local file system. This directly satisfies the requirement for “direct file-access level” mentioned in the question. Cisco documentation and data center architecture guidelines describe NFS as a simple and scalable solution that is widely used for shared storage environments, virtualization platforms, and large-scale data repositories.

NFS operates over standard IP networks, making it easy to deploy without requiring specialized storage networking hardware such as Fibre Channel fabrics. It also supports high-capacity storage systems, enabling centralized file sharing across multiple hosts efficiently.

In contrast, iSCSI, FCoE, and FCP are all block-level storage protocols. These technologies present storage to hosts as raw block devices (disks), requiring a file system to be created on top of them. They do not provide direct file-level access.

Because the question specifically asks for file-level access with simplicity and scalability, NFS is the correct and most appropriate choice.