What is the main idea of this passage? A. Ancient inventions made from iron ore were important to the success of the empires of Egypt, Mesopotamia, and the Kingdom of Kush. B. Ancient civilizations in the Fertile Crescent relied on rivers and harnessed their power to develop into strong and wealthy empires. C. The Kingdom of Kush and Mesopotamia depended on the Egyptians to develop technologies that harnessed the power of rivers. D. Reliance on rivers was the downfall of many ancient empires.