单项选择题
A. Broadband personal comm. Service (PCS)
B. Broadband circuit
C. Infrared
D. Spread spectrum
E. Cable
多项选择题 When you compare the differences between half-duplex and full-duplex Ethernet,which of the following characteristics are exclusive to half-duplex?（）
多项选择题 What are the differences between full-duplex Ethernet and half-duplex Ethernet?（）
多项选择题 Why is full-duplex Ethernet superior to its single-duplex counterpart?（）