b)

Subtractive is to remove as with wood.
Additive is to add to it in small pieces as with clay.
Casting is to make multiple pieces from one original in a mold.
Lost wax (most complicated) is a step in metal casting in that involves making a ceramic mold around a wax sculpture or reproduction of a sculpture in wax and melting out the wax. That leaves a cavity in the ceramic that is then filled with metals such as bronze, silver and gold. The ceramic shell is broken away leaving a reproduction of the wax original, but in metal.