People adapt to great plain regions by locating a near by river because of food and shelter around a substantial stable ecosystems. Which allows high survivability ratings.
What do you mean by supply and demand? you want me to explain what supply and demand is?
Africans was exhausted all options in responding to European imperialism. Some groups tried to shut down Europeans by not trading with them and not allowing missionaries to stay with them.
The United States failure to participate in the newly created League of Nations after World War I resulted in increased isolationism during the 1920's and early part of the 1930's. Many American citizens did not want to be involved in foreign affairs anymore. This is especially true considering the toll in both casualties and cost that World War I had on American citizens and the government. This resulted in the US playing a smaller role in international affairs and a refusal to join World War II until almost 2 years after it officially begins.
