Why Was Mesopotamia an Uninviting Environment for the First Cities

Why was Mesopotamia an uninviting environment for the first cities?

A) The area has no natural defenses.
B) The soil is sandy,temperatures are hot,and the rivers flood unpredictably.
C) The marshy land between the rivers was fertile breeding ground for malaria and other deadly diseases.
D) The rivers are largely unnavigable during long periods of the year,making trade difficult.
E) The region has no forests for timber or usable stone to quarry for building materials.