1. [多选题]Which of the following statements correctly describe the differences between half-duplex and full-duplex Ethernet? (Select two answer choices.)
A. Full-duplex Ethernet uses CSMA/CD to prevent collisions.
B. Half-duplex Ethernet uses a loopback circuit to detect collisions.
C. A full-duplex Ethernet card allows 20Mbps for data transmission.
D. Full-duplex Ethernet makes use of two pairs of wires for data.
E. An Ethernet hub can operate both half and full duplex simultaneously.
2. [单选题]通配符掩码和子网掩码之间的关系是（）。
A. 两者没有什么区别
B. 通配符掩码和子网掩码恰好相反
C. 一个是十进制的，另一个是十六进制(hexadecimal system)的
D. 两者都是自动生成的
3. [单选题]You are given a PC, a router, and a cable. Select the correct combination that will allow you to log into router VE1 locally using a terminal emulation program such as HyperTerminal.
A. Connect the PC's COM port to the router's console port using a straight-through cable.
B. Connect the PC's COM port to the router's console port using a rollover cable.
C. Connect the PC's COM port to the router's Ethernet port using a straight-through cable.
D. Connect the PC's Ethernet port to the router's Ethernet port using a rollover cable.
E. Connect the PC's Ethernet port to the router's Ethernet port using a straight- through cable.
F. F. None of the above
