Three problems of large cities

Poor air and water quality, insufficient water availability, waste-disposal problems and high energy consumption.

Population, air polution, and litter!

Explanation:

Population, air polution, and litter!

Adolf Hitler's final solution was the eradication of the Jewish "problem". She rounded up all undesirables including gypsies Jewish people homosexual, and any person who opposed him politically, and put them into camps. He later was given the idea of using Zyklon B in order to quickly dispose of the prisoners