Delete Model
Deletes all objects from the scene, while retaining the lights, cameras, shaders, and environments, so that you can import a new model into the same scene and shade it immediately.
Delete Model Options
Delete Shaders
Turn this on (default) if you are importing a wire file with materials already assigned to the geometry. Turn it off if you are importing a neutral file format (for example, IGES) so that you can use the materials already in your session.
Delete Lights
Turn this on to remove all the lights in your session. Turn it off to retain the same illumination.