单项选择题
A port in a redundant topology is currently in the blocking state and is not receiving BPDUs. To ensure that this port does not erroneously transition to the forwarding state， which command should be configured to satisfy the requirement？（）
A.Switch（config）#spanning-tree loopguard default B.Switch（config-if）#spanning-tree bdpufilter C.Switch（config）#udld aggressive D.Switch（config-if）#spanning-tree bpduguard
单项选择题 Whichspanning-treecommandwouldcauseaPortFast-enabledinterfacetoloseitsPortFast-operationalstatusanddisableBPDUfilteringifitreceivesBPDUs？（）
单项选择题 Whichofthefollowingconditionsguaranteesthatabroadcaststormcannotoccur？（）
单项选择题 WhichstatementistrueregardingthePortAggregationProtocol？（）
