以下几个步骤对建立工作分解结构排序正确的是( )。 ①确定工作分解结构的结构与编排 ②对工作分解结构的各个组成部分进行编码 ③将工作分解结构的上层分解到下层的组成部分 ④核实工作分解的程度是否必要和已经满足控制要求 ⑤识别可交付成果与有关工作

A．①⑤③②④

B．⑤③①②④

C．⑤①④②③

D．⑤①③②④

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