Which of the following protocols is based on TCP?

The File Transfer Protocol (FTP) is indeed based on the Transmission Control Protocol (TCP). FTP is utilized for transferring files between a client and a server over a network, and it establishes a reliable connection, ensuring that data packets are delivered in order and without loss. TCP is designed to provide such reliable transmission by implementing mechanisms for error checking, data flow control, and retransmission of lost packets, making it suitable for file transfer operations where data integrity is crucial.

In contrast, other protocols listed use different underlying mechanisms. For instance, the User Datagram Protocol (UDP) is connectionless, which means it does not guarantee reliable transmission or ordering of packets. The Dynamic Host Configuration Protocol (DHCP) operates primarily over UDP, as it deals with short, intermittently transmitted messages that can tolerate some loss. Similarly, the Post Office Protocol (POP) is also based on TCP, but it focuses more on email retrieval rather than file transfers. Therefore, while FTP is the correct answer as it relies on TCP for its operations, recognizing the characteristics and purposes of the other protocols helps distinguish TCP-based functionality.