单项选择题
Which of the following WAN protocols is a packet switching technology?（）
A.Frame Relay B.POTS C.PSTN D.ISDN
单项选择题 Using network monitoring tools would allow an administrator to do which of the following?（）
单项选择题 Determining when to retransmit frames is an example of which of the following Ethernet properties?（）
单项选择题 Which of the following address formats uses 32-bit addressing?（）
