The correct answer is (c) TELNET.
TELNET is a network protocol that allows a user to log in to a remote computer and interact with it as if they were sitting at the computer’s console. It is a text-based protocol, which means that all communication between the client and server is in the form of text.
FTP (File Transfer Protocol) is a protocol that allows users to transfer files between two computers on a network. It is a relatively simple protocol, and it is often used to transfer files between a client computer and a server computer.
UDP (User Datagram Protocol) is a connectionless protocol that is used to send datagrams between two computers on a network. Datagrams are small packets of data, and they are not guaranteed to be delivered in order or at all.
RAR is a file archive format that is used to compress and archive files. It is a popular format for archiving large files, and it is often used to share files over the internet.
TELNET is the only protocol that is used for remote login. FTP, UDP, and RAR are not used for remote login.