The increasing percentage of urban dwellers in more-developed countries is best
explained by

heat from the core of the earth causes convection currents to occur in the mantle. these currents slowly move the crust around.

chinese civil war took place over a long period of time between 1927 and 1950. the war was interrupted when japan invaded china in 1936 and by world war ii. the war was fought between the nationalist government of china, also called the kuomintang (kmt), and the communist party of china (cpc).