The correct answer to this open question is the following.
How could the mountains to the north benefit ancient Mesopotamians?
The mountains to the north benefited ancient Mesopotamians in the following way.
Those large mountains served to provide fresh water to the rivers with the melting of the ice. In times of rain, streams from the mountain ended up into the rivers Tigres and Euphrates.
That is why early Sumerians could grow good crops because the land was so fertile due to the flooding of both rivers, leaving fertile soil ready to produce crops. Sumerians developed advanced agriculture techniques that helped them to establish important city-states such as Kisk, Ur, Uruk, Lagash, Nippur, and Eridu.