(A) the US couldn’t remain neutral anymore
(B) Germany’s submarine warfare
(C) economic and political ties to Great Britain
(D) ** the assassination of Archduke Ferdinand
EXPLANATIONS BELOW
Concept note-1: -The assassination set off a rapid chain of events, as Austria-Hungary immediately blamed the Serbian government for the attack. As large and powerful Russia supported Serbia, Austria asked for assurances that Germany would step in on its side against Russia and its allies, including France and possibly Great Britain.
Concept note-2: -The assassination of Archduke Franz Ferdinand was the immediate cause of a war between two great powers-Russia and the Habsburg Austro-Hungarian Empire.
Concept note-3: -What were the main reasons for U. S. involvement in the war? The main reasons the US got involved in the war was because of nationalism, imperialism, militarism, and forming allies.