Correct Option: D

Wrought iron is an iron alloy with a very low carbon content in contrast to steel, and has fibrous inclusions, known as slag. This is what gives it a “grain” resembling wood, which is visible when it is etched or bent to the point of failure. Wrought iron is tough, malleable, ductile and easily welded. Historically, it was known as “commercially pure iron”; however, it no longer qualifies because current standards for commercially pure iron require a carbon content of less than 0.008 wt%. Wrought iron is the purest form of commercial iron, containing 0.10% to 0.25% of carbon and less than 0.25% of impurities like sulfur, phosphorus, silicon and manganese. Wrought iron is redshort if it contains sulfur in excess quantity. It has sufficient tenacity when cold, but cracks when bent or finished at a red heat. It is therefore useless for welding or forging.