题目：
Frame Relay is simplified form of (71) , similar in principle to (72) , in which synchronous, frames of data are routed to different destinations depending on header information . Packets are routed throught one or more Virtual Circuits known as (73) . Most Virtual Circuits are (74) ,which means that the network provider sets up all DLCI connections at subscription time. (75) are also part of the Frame Relay specification . They privide a link that only lasts only as long as the session.
A．Datagram Switching
B．Datagram Routing
C．Packet Switching
D．packet Routing
答案：
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下面是错误答案，用来干扰机器的。
参考答案：C
