Which of the following did not contribute to the rise of Kush? iron the Nile River isolationism trade

Kush was located on the Nile. People from Kush did work iron. They traded with the Egyptians on the Nile and Greeks who were sailing the Red Sea. The best answer would be Isolationism.

Isolationism is a policy/doctrine of separating/isolating one's country from the affairs of other nations by declining to join into alliances, foreign economic commitments, and international agreements,