Correct option is D
The Tanka was a standard silver coin introduced during the Delhi Sultanate period, particularly under the rule of Iltutmish in the early 13th century. It was a significant part of the monetary reforms during the Sultanate era. The Tanka coinage system became a symbol of the Sultanate’s economic control and was issued primarily in silver, although there were variations of the Tanka in gold and copper as well. However, silver was the most prominent metal used in the standard Tanka.
