Why did the first cities arise in southern Mesopotamia?

Because it was a very fertile land, thats why it is caled "The Fertile Cresent".

Explanation:

peasants’ war, (1524–25) peasant uprising in germany inspired by changes brought by the reformation, peasants in western and southern germany invoked   divine law to demand agrarian rights and freedom from oppression by nobles and landlords. as the uprising spread, some peasant groups organized armies. although the revolt was supported huldrych zwingli and thomas müntzerits condemnation by martain luther contributed to its defeat, principally by the army of the swabian league. some 100,000 peasants were killed. reprisals and increased restrictions discouraged further attempts to improve the peasants’ plight.

i think it would be " a" i might be wrong tho

i see, would you mind putting it as one?