The best answer is B. According to historical estimates, irrigation using river water began at about the same time in Egypt and Mesopotamia around 6000 BC using the water of the Nile and Tigris /Euphrates rivers respectively. The first successful efforts to control the flow of water were made in Mesopotamia and Egypt where the remains of the prehistoric irrigation works still exist. In Ancient Egypt, the construction of canals was a major endeavor of the pharaohs and their servants.