The water of the Tigris and Euphrates rivers flows slowly from the northwest to the southeast. What does this slow water flow allow for?
a
Collection of silt, which can be stored and used as food
b
Collection of silt, which acts as fertilizer
c
Collection of clay to be used by the Egyptians for cuneiform writing
d
Collection of clay to be used by Sumerians for hieroglyphic writing
