单项选择题
A.DCC1-3B.K1/K2C.E1/E2D.DCC4-12
A.Tail endB.Head endC.Source endD.Sink end
A.向下游发AIS,向对端发RDIB.向下游发AIS,向对端发REI误码指示C.向下游发REI误码指示,向对端发AISD.向下游发SSF指示,向对端发RDI