[Gpsbabel-misc] discrete vs. connected points

[<nt....@gm...>]

  Google-earth displays one of my gpsbabel-generated files half with
discrete points, half with lines linking each point to its successor.
There is no obvious (for me) reason why this should be so when browsing the
source file (gpx) or the kml file used by google-earth. To obtain discrete
points overall, I tried this :

# gpsbabel -i gpx -f a.gpx -x transform,wpt=trk -o kml -F a.kml

and other variants ; to no avail.
  What is the correct invocation for obtaining a kml file which is rendered
as discrete points by google-earth ?
  Thank you very much. -Nicolas