All of the following commands could be used to verify availability of tty devices on the system EXCEPT：（）。

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

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

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