Germany was forced to agree to the "War Guilt Clause" as part of the Treaty of Versailles. This meant --

Austria-Hungary took full responsibility for starting World War I and agreed to pay the Allied Powers war reparations

Germany took full responsibility for starting World War I and agreed to pay the Central Powers war reparations

Germany took full responsibility for starting World War I and agreed to pay the Allied Powers war reparations

Austria-Hungary took full responsibility for starting World War I and agreed to pay the Central Powers war reparations