单项选择题
A. defines how the media is accessed
B. supplies a token to determine which host has access to the media
C. defines the encoding of electrical signals on the wire
D. determines the preamble bits
单项选择题 What value is primarily used to determine which port becomes the root port on each non root switch in a spanning-tree topology?（）
单项选择题 What is the purpose of the OSPF router ID in a OR/BOR election?（）
单项选择题 A network administrator needs to verify that switch interface 0/5 has been assigned to the Sales VLA.N. Which command will accomplish this task?（）