Washington may have saved republican government in america in 1783 when he

The choices were 
A) refused to back Continental officers' demands at Newburgh
B) persuaded Maryland to ratify the Articles of Confederation
C) negotiated the peace treaty with Britain
D) put down a slave uprising

The answer is A. 

George Washington was the Commander-in-Chief who sought the support of the Continental Army in Congress. There was a reported Newburgh Conspiracy that planned for a coup last 1973 because of the unpaid wages. The Congress, in the end, made a compromised agreement about this issue.