[单选题]TCP23是（）协议端口号；UDP69是（）端口号；TCP80是（）端口号。

正确答案 ：C

TELNET TFTP HTTP

[单选题]OSPF骨干区的区域编号为（）

正确答案 ：C

0.0.0.0

[多选题]With regard to Ethernet media access methods, which of the following are true?(Choose all that apply.)

正确答案 ：BC

A device listens and waits until the media is not busy before transmitting.

All devices on an Ethernet segment see data that passes on the network medium.

解析：解析：Explanation:

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