Which two statements about the various implementations of STP are true？（）
- Amon Spanning Tree maintains a separate spanning-tree instance for each VLAN configured in the network.
- BThe Spanning Tree Protocol （STP） is an evolution of the IEEE 802.1w standard.
- CPer-VLAN Spanning Tree （PVST） supports 802.1Q trunking.
- DPer-VLAN Spanning Tree Plus（PVST+） is an enhancement to 802.1Q specification and is supported only on Cisco devices.
- ERapid Spanning Tree Protocol （RSTP） includes features equivalent to Cisco PortFast， UplinkFast， and BackboneFast for faster network reconvergence.
- FMultiple Spanning Tree （MST） assumes one spanning-tree instance for the entire Layer 2 network， regardless of the multiple number of VLAN