磁力脱水槽底部塔形磁系磁场强度沿轴向分布情况是上部强,下部弱。
参考答案:错
家兔具有( )
A.门齿与犬齿
B.犬齿和臼齿
C.门齿和臼齿
D.门齿、犬齿和臼齿
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.Permanent Circuits
B.Permanent Virtual Circuits
C.Switched Virtual Circuits
D.Switched Circuits