单项选择题
Which layer of the OSI reference model uses the hardware address of a device to ensure message delivery to the proper host on a LAN?（）
A. physical B. data link C. network D. transport
单项选择题 Which option is a valid IPv6 address?（）
单项选择题 What is known as "one-to-nearest" addressing in IPv6?（）
单项选择题 Which type of cable is used to connect the COM port of a host to the COM port of a router or switch?（）
