Which of the following processes is a type of finishing in secondary processing?

Finishing processes in secondary processing are applied to enhance the surface quality, aesthetic appeal, and function of a product after its initial formation. Painting is a prime example of a finishing process because it involves applying a layer of paint to a surface. This layer not only improves the appearance of the product but also provides protection from environmental factors such as moisture and UV exposure. Painting contributes to the final presentation and functionality, enhancing both the durability and visual appeal of materials.

Other processes like extrusion, welding, and drilling have different primary purposes. Extrusion is typically associated with shaping materials by forcing them through a mold, while welding is used to join two pieces of material together. Drilling, on the other hand, is focused on creating holes in a material. Although these processes may involve changes to the workpiece, they do not specifically enhance the surface quality or provide a finishing touch in the same way painting does.