In the following essay, each blank has four choices. Choose the most suitable one from the

four choices and write down in the answer sheet.

A socket is basically an end point of a communication link between two applications. Sockets that extend over a network connect two or more applications running on(66)computers attached to the network. A socket(67)two addresses:(68). Sockets provide a(69)communication channel between one or more systems.

There are(70)sockets separately using TCP and UDP.

A．unique

B．separate

C．same

D．dependent