Where did the highest concentration of cities in mesopotamia emerge?
a. areas of high ground, away from the dangerous riverbanks
b. areas where the tigris and the euphrates flowed closely together and
intersected
c. mountainous areas, which offered protection from heavy winds and rainfall
d. cavernous areas that were a day's walk from river deltas

B. Areas where the Tigris and the Euphrates flowed closely together and

intersected

Explanation:

The people in Mesopotamia relied heavily on the rivers Tigris and Euphrates. The climate there is dry and hot so they needed the flooding of the two rivers in order to fertilize the soil for the crops. They made watering systems and mechanisms for lowering and raising the water in those systems for better crop growing. Without the two rivers, a civilization would never have been born there.

i would think it's industries and hydroelectric power