下列关于政府收费说法不正确的是( )。

A．它是一种国民收入分配和再分配行为

B．是管理经济和管理社会的重要手段之一

C．是以单位为主体的行使国民收入分配和再分配的手段之一

D．合理的政府收费应该是在消费上具有竞争性的公共服务

SDLC was invented by IBM to replace the older Bisynchronous protocol for wide area connections between IBM equipment. A varietion of the (71) protocol called NRM is essentially the same as SDLC. SDLC is (72) protocol like HDLC, Frame Relay or X.25.An SDLC network is made up of (73) that controls all communications, and (74) . It is capable of (75) operation, but almost all practical applications are strictly half duplex.

A．half duplex

B．full duplex

C．half or full duplex

D．half and full duplex