Which statement correctly describes the extended system ID?

Which statement correctly describes the extended system ID?

A.
It is a bridge MAC address which is allocated from a pool of MAC addresses that are factory
assigned.

B.
It is the VLAN identifier value and allows for 4096 BIDs to be uniquely identified.

C.
It is the 2-bit number of the MSTP instance.

D.
It is a hex number used to measure the preference of a bridge in the spanning-tree algorithm.