WhichstatementcorrectlydescribestheCiscoimplementationofRSTP?()

A.PortFast，UplinkFast，andBackboneFastspecificconfigurationsareignoredinRapidPVSTmode.

B.RSTPisenabledgloballyandusesexistingSTPconfiguration.

C.Rootandalternativeportstransitionimmediatelytotheforwardingstate.

D.Convergenceisimprovedbyusingsub-secondtimersfortheblocking，listening，learning，andforwardingportstates.