D.) United Nations, because the league of nations was ineffective and basically caused WWII
 
have a nice day <3  
        
                    
             
        
        
        
After World War 2 Germany was dived into half. The western half was under American control and the Eastern half was under Russian control. Berlin lay in the Western half and was divided between Russia and America, meaning that East Berlin was an island of Russian controlled Germany surrounded by areas under American control. Russia was a communist country and people from East Berlin tried to flee to West Berlin and so the Berlin Wall was built to stop this.Until the east Germans were rescued by pink Floyd!
        
             
        
        
        
Antietam is the bloodiest day in American history
        
             
        
        
        
First, they made settlement of the West possible after the Civil War by connecting farmers (and miners, ranchers, loggers, and others) to markets. 
 Second, railroads helped to integrate different regions of the country economically. 
 
        
                    
             
        
        
        
I would say it would either be racism or discrimination.
Hope it helps.