German Submarines Began Sinking Unarmed and Unresisting American and British

German submarines began sinking unarmed and unresisting American and British merchant and passenger ships without warning

A) because they were violating international law by operating in a war theater.
B) in retaliation for the British naval blockade of Germany.
C) in an effort to keep the United States out of the war.
D) because international law now allowed this new style of warfare.
E) in a last-ditch effort to win the war.