Final answer:
The welding method described is Spot Welding, which is efficient, fast, and does not require a filler but produces spot welds of lower strength.
Step-by-step explanation:
The welding method characterized by not requiring a filler material, having a fast process time (less than a second for the weld and a few seconds to place the clamp), the potential for both automated and manual operation, and a reputation for producing spot welds that are not particularly strong and pose difficulties when welding some other metals, is known as Spot Welding (Option D).
Spot welding is a resistance welding technique that mainly joins sheets of metal. The pieces are fused together by the heat generated from the resistance to the flow of electric current through the metal pieces and the force applied to hold them together. It has been widely used in various industries, such as automotive and manufacturing, for its efficiency and speed, and because it does not generally require additional materials in the form of filler.