单项选择题

For each blank, choose the best answer from the four choices and write down on the answer sheet.
(71) is a channel’ s capacity which directly reflects the data transfer rate of the channel.
(72) functions in a NetWare network which is used to define addressing schemes.
(73) is a network layer device that supports multiple LAN interfaces and segments LANs into smaller collision and broadcast domains.
(74) is the popular LAN developed under the direction of the IEEE802.3.
(75) is a device which enables digital microcomputers to communicate across analog telephone lines.