由于距离继电器都要反映补偿电压或其它由电压与电流组成的复合电压，故为了做出它们的相量不仅要确定电压和电流的相位，但不要确定它们的幅值

TCP/IP (71) layer protocols provide services to the application (72) running on a computer. The application layer does not define the application itself, but rather it defines (73) that applications need-like the ability to transfer a file in the case of HTTP. In short，the application layer provides an (74) between software running on a computer and the network itself．The TCP/IP application layer includes a relatively large number of protocols，with HTTP being only one of those．The TCP/IP (75) layer consists of two main protocol options-the Transmission Control Protocol(TCP)And the User Datagram Protocol(UDP)．

A．application

B．transport

C．link

D．network