Which of the following is TRUE about the ping  -f command?（）

A.It is useful for diagnosing data dependent problems by filling the packet with the byte pattern following the f in the command line.

B.It is useful for flooding from slow character based terminals since it only displays a dot . for each packet sent in fast mode.

C.It is useful for flooding from slow character based terminals since it only displays a dot .       for each packet sent and a backspace on returned in fast mode.

D.The command can only be run by root.