The correct options are
A Humiliation of Germany at the Paris Peace Conference.
C Japan was ignored at the Treaty of Versailles.
D Groupism and militarism.
The root cause of the Second World War lay in the Treaty of Versailles. Germany was made to lose its territories and pay heavy indemnity as war reparations. Japan was ignored largely and not rewarded for having won the First World War on the side of the Allies. Hence, groupism and militarism formed among these countries.