Which of the following will flush all print jobs on all configured queues of the system?

A.
lprm -a all

B.
lprm -all

C.
lprm -a *

D.
lpflush -all

Explanation/Reference:
from the man pages:
lprm – remove jobs from the line printer spooling queue
SYNOPSIS
lprm [ -a ] [ -A ] [ -Ddebugopt ] [ -Pprinter ] [ -V ] [ -Uuser ] [ jobid…  ] [ all ]
       -a   Remove files from all spool queues available to the user.