In what
ways did the rivers support
agriculture and the city-states?

when rivers flooded, they brought fertile soil. they also provided water for crops.

Explanation: this helped the people grow crops and gave them soil to grow more.

wood carving remains today the primary sculptural art form of the sub saharan continent. african art history shows the earliest wooden sculptures from the 17th c are attributed to the kuba, central zaire but the earliest surviving sub-saharan sculpture is a zoomorphic head found in 1928 in central angola.

i hope this .

since most of current immigration into the u.s., both legal and illegal, is coming from latin america. it would be very difficult to imagine or rationalize a country my fellow citizens are trying desperately to flee into, would pose a threat to my prosperity or freedom. since the u.s. has a long history of intervention, but no record of permanent occupation, i would not feel oppression is the main objective.  

the largest free trade nation, along with the largest gdp in the world wanting to expand it's economic policy on us, and including us, could only be positive. the u.s. government has no interest in, or way of simply forcing american culture on us. and has no track record of it. other nations that adopted american social culture, or "americanization" did so voluntarily, mainly through the choice of allowing american businesses and u.s. citizens to come into their nations, as free operatives.