Which of the following statements is true regarding TCP port 21?

TCP port 21 is indeed used for handling FTP (File Transfer Protocol) control commands. FTP is a standard network protocol used for transferring files between a client and server. The operations associated with FTP, such as starting the connection, logging in, and issuing commands for file transfers, are managed over TCP port 21. This port is specifically designated for the FTP control connection, which allows the exchange of commands between the client and server.

In contrast to the other options, which refer to different protocols and their respective ports: TCP port 22 is used for SSH, port 23 is associated with Telnet, and port 80 is used for HTTP traffic. Understanding the specific role of TCP port 21 within the context of FTP is essential for recognizing how file transfers and commands are structured in network communications.