Final answer:
The answer to the question is Autogenous welding (A), which is a technique of joining metals without the use of filler metal.
Step-by-step explanation:
The question pertains to a specific type of welding operation. The correct answer to the question, "A fusion welding operation in which no filler metal is added is called what?" is A) Autogenous welding. This technique involves joining metals together by melting and fusing them without adding any additional filler material. In contrast, Oxyacetylene welding, Submerged arc welding, and Gas metal arc welding often use a filler material to join the metal pieces.
Welding has been a crucial fabrication process for joining metal materials, with a history of use by blacksmiths in forge welding to bind iron and steel. The process utilizes various heat sources like gas, electricity, and laser to achieve the desired weld.