Running DraftSight 1R4 x64

I recently imported an AutoCAD dwg file from a surveyor who was using AutoCAD Civil 3D - note, there were no 3D entities in the file.   Everything has imported OK.  However, now I want to delete some of the entities in the Model space but can't seem to do so.  When I do a List on the entities, they say they're a "ACAD PROXY ENTITY."  I tried everything........delete entity, delete layer, etc., etc. and have searched the Help menu extensively but still to no avail.  I'm sure this is simple.   Note, I'm only a beginner w/ DS and have had only about 1 year experience w/ AutoCAD Lt