Answer:
c. to protect inhabitants of the city-state from attack
Step-by-step explanation:
Many ancient civilizations had walls around their cities and city-states to protect themselves from foreign attacks.
In ancient times, attacks on other civilizations or cities were a frequent occurrence, as societies often fought over the land and the goods they provided. In Mesopotamia, people wanted to protect themselves from Ur attack. As the cities weren’t that big and elaborated as today, it was possible to surround them with fortification.
This kept the enemies outside of the city and delay their aggression. There was also the possibility to strategically place the military along the walls, so they could observe the outside territory and guard the city, attacking the unwanted intruders during their break-in. People would be much safer in places surrounded by walls.