A.nTransport plane
B.nMaintenance plane
C.nControl plane
D.nManagement plane
A.nloopback check
B.nlinktrace check
C.nconnectivity verificatio
D.nservice consistency check
A.What young people saw and heard
B.What young people see and hear it
C.What does young people see and hear
D.What young people see and hear
A.Declarative
B.Imperative
C.Exclamatory
D.Interrogative
A. Background information
B.Current situation
C.Significance of the topic
D.Literature review