The verified response to “Ancient History question: Which metal was unknown to the Harappans?” is Iron, option C. The original question-specific evidence states: Harappans used copper, bronze, gold and silver, but not iron. Iron is the correct answer to “Which metal was unknown to the Harappans”. This evidence connects the required Ancient History fact with its archaeological, geographical, cultural or chronological setting. The choices Gold, Copper and Silver do not satisfy the same combination of site, feature, river region, crop, craft, discovery, chronology or cultural association. Replaying that method confirms Iron as the keyed response for this Ancient History question.