Answer : Chemical energy to thermal energy
Explanation : When the welding torch uses the acetylene fuel for producing flame it is using the chemical acetylene to generate energy in form of light, after the flame is produced the fuel is used for melting a metal which is utilizing the thermal energy. So the ultimate final product is generated from chemical to thermal and so the energy transformation is from chemical energy to thermal energy.
Nails are made up of iron not of phosphorus and barium.
As both phosphorous and barium are relatively weaker than iron ,phosphorus breaks easily and barium is also fairly weak. Iron nails are already also not that strong, but their weight and strength are sufficient.
So the nails are made up of iron.
I believe it means idea because a Web is out line to a a more structured idea
