Correct Option: D

socket() creates a new socket of a certain socket type, identified by an integer number, and allocates system resources to it. bind() is typically used on the server side, and associates a socket with a socket address structure, i.e. a specified local port number and IP address. listen() is used on the server side, and causes a bound TCP socket to enter listening state. connect() is used on the client side, and assigns a free local port number to a socket. In case of a TCP socket, it causes an attempt to establish a new TCP connection. When connect() is called by client, following three way handshake happens to establish the connection in TCP.
(1) The client requests a connection by sending a SYN (synchronize) message to the server.
(2) The server acknowledges this request by sending SYN-ACK back to the client.
(3) The client responds with an ACK, and the connection is established.