The correct option is D Mesopotamia
The Indus Valley people had trade relations with Mesopotamia. The trade relationship during the later 3rd millennium was a direct one , ship from Meluhha docked in Mesopotamian ports , some Meluhhans settled in Sumer, and there is a seal belonging to a Mesopotamian whose job it was to act as an interpreter of the Meluhhan language. On the other hand , people from Mesopotamia reached the Indus , so it is clear that the Harappans conducted the trade between two civilizations.