Which two statements are true when the extended system ID feature is enabled？ （）
- AThe BID is made up of the bridge priority value（two bytes） and bridge MAC address （six bytes）.
- BThe BID is made up of the bridge priority （four bits）， the system ID （12 bits）， and a bridge MAC address （48 bits）.
- CThe BID is made up of the system ID （six bytes） and bridge priority value （two bytes）.
- DThe system ID value is the VLAN ID （VID）.
- EThe system ID value is a unique MAC address allocated from a pool of MAC addresses assigned to the switch or module.
- FThe system ID value is a hex number used to measure the preference of a bridge in the spanning-tree algorithm.