单项选择题
A.a root port being transitioned to the blocking state
B.a port being assigned as a root port
C.a port being assigned as an alternate port
D.a root port being transitioned to the forwarding state
单项选择题 IEEE802.1wisaRapidSpanningTreeProtocol（RSTP）thatcanbeseenasanevolutionofthe802.1standard.Whataretheportrolesdescribedby802.1w？（）
单项选择题 Forthefollowingports，whichportisoneverybridgeinaSpanningTreeProtocolIEEE802.1wnetworkexcepttherootbridge？（）
单项选择题 Whatarethe"boundIPaddresses"usedforinLDP？（）