The correct answer is C) floods provided water for crops.
Early settlements first developed along rivers because floods provided water for crops.
Water is vital for humanity. For the early humans was the same. They had to settle in next to the rivers in order to have enough water to drink and to use it for irrigation purposes. That was the case of important ancient civilizations such as the Sumerians, who settled in the middle of two rivers in the Middle East. the Tigris and Euphrates. This was also the case of the Egyptians who settled in next to the Nile River.
The other options were a) people could use tools to dig ditches, b) plants and animals were more abundant, and d) people could mine for copper and gold.