多项选择题 Identify three valid host addresses in the 192.168.27.0 network with a subnet mask of 255.255.255.240. （）

单项选择题 You are upgrading your Cisco router IOS from a TFTP server over the network. The upgrade procedure is stopped and you are prompted to erase the current flash contents before continuing. What is most plausible reason for this? （）

单项选择题 At Layer 2 of the OSI model, which component connects a host to the network media?（）