INDIAN HISTORY

Detailed explanation-1: -Gold, copper, silver, bronze metals were known to Indus Valley Civilization but not iron. The Indus valley people or Harappan people not discovered iron.

Detailed explanation-2: -Cow, camel, horse, and lion were not depicted on seals. Unicorn (bull) was the animal most commonly represented on the seals. In fact, horse was an animal that was unknown to the Harappan Civilization.

Detailed explanation-3: -The correct answer is option 4 i.e Iron, The people of the Harappan sites (also known as the Indus valley) had the knowledge of using bronze, copper, silver, and gold but they did not use iron. Hence it is not yet discovered from the sites.