The correct option is D Wootz steel
Tippu Sultan's sword was made up of the Wootz steel, which was manufactured in Southern India. Wootz Steel is produced
by a method known in ancient India. The process involved preparation of
porous iron, hammering it while hot to release slag, breaking it
up and sealing it with wood chips in a clay container, and heating it until the
pieces of iron absorbed carbon from the wood and melted. The steel thus
produced had a uniform composition of 1–1.6% carbon and could be heated and
forged into bars for later use in fashioning articles, such as the famous medieval
Damascus swords.