"Sumerian city-states fought each other" would be the best option from the list, since this internal division led to a collapse of power that left people without protection or a solid economy.
No, the North had a bigger population because there was more toleration there which attracted more immigrants and settlers there.
social: the spanish had the monarchy government. this affected because they got to the americas and stablished a king's representant changing the lifestyle of the people that was there before them and also the natives were treated like slaves and a minor race.
Religious: the Spanish practiced catholicism in that time also stablishing it as the only religion you could practice, changing native's lifestyle.
that is all with i can help with :D
nice day!
Emperor Romulus Augustus was deposed by the Germanic King Odoacer if I remember correctly.