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 (31) computers attached to the net-work. A socket (32) two addresses: (33) . Sockets provide a (34) communication channel between one or more systems. There are (35) sockets separately using TCP and UDP.

A．full-duplex

B．half-duplex

C．simplex

D．complex

有人说：没有规矩，不成方圆。但也有人说：改革创新就要打破常规。你对此有什么看法？