What does a rigid PCB start out as before any pattern is made?

Select one answer.

• A completely finished manufacturing panel that already holds many separate individual boards on it and only needs to be carefully cut apart into the separate pieces.
• A block of solid copper that is later hollowed out to leave the insulation.
• Copper-clad laminate — an insulating sheet with copper foil bonded to one or both faces.
• A bare sheet of glass-epoxy with no copper on it at all.