单项选择题

Whichstatementistrueaboutthecomponentsofaqueuingmechanism?()

A.Eachsubinterfacehasitsownhardwarequeueandcanexperiencecongestionjustlikeitsmaininterface
B.Hardwarequeuingisonlyusedifthesoftwarequeuesareexperiencingcongestion.
C.Hardwarequeuesandsoftwarequeuesarenotusedconcurrently.
D.ThehardwarequeuingsystemalwaysusestheFIFOqueuingmechanism.