ANS:B - Chemical energy.

Thermit welding uses chemical energy as the energy source. Thermit welding, also known as thermit fusion welding, is a type of welding process that utilizes a chemical reaction between a mixture of metallic powders, typically aluminum powder and iron oxide (commonly known as rust), to produce intense heat. This chemical reaction, known as the thermite reaction, generates extremely high temperatures, reaching temperatures of around 2500°C (4500°F) or more. During the thermite reaction, the aluminum powder reacts exothermically with the iron oxide, producing molten iron and aluminum oxide as byproducts. The heat released during this reaction is utilized to melt and fuse the metals being welded together, creating a strong metallurgical bond between them. Therefore, thermit welding relies on chemical energy released from the exothermic reaction between the metallic powders to generate the heat required for welding, rather than relying on electrical energy, high velocity electrons, or frictional heat.