(A) Germany’s policy of unrestricted submarine warfare
(B) ** United States entry into World War 1
(C) Interception of the Zimmerman telegram
(D) The sinking of the Lusitania
EXPLANATIONS BELOW
Concept note-1: -What was the main cause of World War I? World War I began after the assassination of Austrian archduke Franz Ferdinand by South Slav nationalist Gavrilo Princip on June 28, 1914.
Concept note-2: -Wilson cited Germany’s violation of its pledge to suspend unrestricted submarine warfare in the North Atlantic and the Mediterranean, as well as its attempts to entice Mexico into an alliance against the United States, as his reasons for declaring war.
Concept note-3: -The US entered World War I because Germany embarked on a deadly gamble. Germany sank many American merchant ships around the British Isles which prompted the American entry into the war.