A gateway machine has access to the Internet and is trying to reach a machine on the Internet called cactus.org. Although the gateway machine cannot reach cactus.org， another network across town is able to reach cactus.org. Furthermore， the gateway machine can reach the network across town， but cannot ping the cactus.org. Which of the following tools will best help diagnose the location of the problem？（）

单项选择题Whichofthefollowinglocalfilesisusedtorunthedatecommandontheremotemachine Earth usingthefollowingrexeccommandwithoutrequestforapassword？rexecEarthdate（）。

A.~/ .rhosts
B.$HOME/.netrc
C./etc/hosts.equiv
D./etc/security/user

单项选择题AllofthefollowingcommandscouldbeusedtoverifyavailabilityofttydevicesonthesystemEXCEPT：（）。

A.lstty
B.lscons
C.lsdev
D.lscfg

单项选择题Whatisthepurposeof etc uucp Devices？（）

A.Defines permissions for remote machines contacting the local machine through BNU
B.Specifies dialer and modem types for uucp connections
C.Defines basic communication parameters
D.Assigns alternate or additional Systems， Devices and Dialers files

单项选择题Whichofthefollowingcommandsgathersnetworkpacketstatistics？（）

A.netstat -i
B.ifconfig -a
C.errpt -a
D.iptrace -i

单项选择题Whichofthefollowingflowcontrolsettingsallowsresumptionofsuspendedoutputbyhittingthe R key？（）

A.XON/XOFF
B.NONE
C.RTS/CTS
D.XON/IXANY