Refer to the exhibit． Why has this switch not been elected the root bridge for VLAN1?

A、 It has more than one interface that is connected to the root network segment．
B、 It is running RSTP while the elected root bridge is running 802．1d spanning tree．
C、 It has a higher MAC address than the elected root bridge．
D、 It has a higher bridge ID than the elected root bridge．

【正确答案】 D

【答案解析】考点：考查STP选举原则，RID小者优先。由提示可知根桥的RID为20481
A：有超过1个接口连接到根网段，错误
B：使用了RSTP，但是选举根桥时使用了802．1d，错误
C：比根桥有更高的MAC地址，错误
D：比根桥有更高的RID，正确。