What is significant about the yearly flooding of the Nile Valley? (1 point)
a. The floods typically killed many people, making it hard to live in the valley; most people moved to the mountains above the riverbed.
b. It is the only geographic disadvantage of the area.
c. It replenished the nutrients in the soil, making the valley very fertile.
d.It prompted the Egyptians to build enormous pyramids to escape the floodwaters.