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．DLCIs

B．HDLCs

C．SDLCs

D．DLs

关于书眉版式设计的说法，正确的有（）。

A.应该双码面排章名，单码面排书名

B.图书各章开始的第一面可不印书眉

C.一般要设置书眉线与版心相隔

D.书眉所用字号应该小于正文主体文字

E.书眉可以都齐左排，或都齐右排