The correct answer is D. All the above.
Blisters in the finished wrought iron are caused due to the reaction between oxide of iron and carbon. This reaction is called oxidation. When iron is heated in the presence of oxygen, it reacts to form iron oxide. This reaction is exothermic, which means that it releases heat. The heat from the reaction causes the iron oxide to expand, which can cause blisters to form on the surface of the iron.
The edges of a finished wrought iron are rough due to red shortage. This is because the iron is not heated evenly during the forging process. The edges of the iron are heated more than the center, which causes them to expand more. This expansion causes the edges of the iron to become rough.
Pig iron (charcoal) is manufactured from magnetic ore (Fe3O4). This is done by heating the magnetic ore in a furnace in the presence of carbon. The carbon reacts with the oxygen in the magnetic ore to form carbon monoxide. The carbon monoxide then reacts with the iron in the magnetic ore to form pig iron.
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