Which of the following represents a storage protocol that operates over standard TCP/IP networks at the file system level?

The correct answer, representing a storage protocol that operates over standard TCP/IP networks at the file system level, is Network Attached Storage (NAS). NAS is specifically designed to provide file-level storage services, allowing multiple clients to retrieve and store files over a network using standard protocols like NFS (Network File System) or SMB (Server Message Block). This file-oriented approach makes NAS a flexible and easy solution for environments where file sharing and collaboration are critical.

Fibre Channel is a high-speed networking technology primarily used for storage area networks (SANs) that operates at the block storage level, not file level, and does not utilize standard TCP/IP.

Block storage refers to storage that manages data as blocks, typically used in SANs and is not inherently reliant on TCP/IP networks for its operation, as it typically uses other transport protocols. Similarly, iSCSI is a protocol that enables block storage devices to communicate over standard TCP/IP networks but does not operate at the file system level like NAS does. Thus, NAS stands out as the ideal choice for applications requiring file-level access over standard TCP/IP networks.