President Harding made a separate peace with Germany to end the war was the main reason to reject the Treaty of Versailles.
Answer: Option A
Step-by-step explanation:
In the year 1921, the president of United States at that time Warren G. Harding decided to make peace with the German in order to stop the world war one. Harding strongly believed that the Treaty of Versailles will not bring peace and will not be helpful in any way to end the World War 1. Thus Harding rejected the Treaty of Versailles and agreed to sign the U.S – German peace treaty in the same year 1921.