单项选择题
A.193.130.56.0
B.198.37.16.15
C.198.130.16.15
D.198.130.56.15
单项选择题 Ahostisexpectedtobeamailrelayorreceivingendpoint.Whichofthefollowingdaemonsshouldbelisteningforconnectionsonport25？（）
单项选择题 Amachine’sONLYexternalinterfaceisconfiguredwithanaddressof192.168.5.1andanetmaskof255.255.255.0.Noslotsareavailableforexpansion.Whichofthefollowingproceduresshouldbeperformedtomakeitfunctionasagateway？（）
单项选择题 Allofthefollowingcommandscanbeusedtoplaceaninterfaceintothe"down"stateEXCEPT：（）。