I would say the answer is the answer is D…
        
             
        
        
        
At Promontory Summit, Utah Territory.
        
                    
             
        
        
        
The nation that joined the war in 1917 was the United states but not necessarily as part of the allies, rather America had opted to fight Germany, an enemy of the allies, more as an associate ally to protect its own interests.
American went to war to stop German aggression and spread values of democratic freedom and made decisive contributions to the final battles of 1918.
The Americans decided neutrality would not do when German aggression on the high seas went on to such an extent that it threatened U.S. national security, and so the Germans had to be stopped. 
 
        
             
        
        
        
Answer:
  A. Private families supported large armies.
Explanation:
Heian government came to rely on the private armies instead of their own army.
The increase in the private families’ power led to the growth of two of Japan’s greatest warrior clans, the Taira and the Minamoto.