Answer: D. the policy of unrestricted submarine warfare
Step-by-step explanation:
The picture used here represents the sinking of the Lusitania, which occurred on May 7th, 1915. This attack was part of Germany's use of unrestricted submarine warfare during the war. In February of 1915, Germany had announced that it would be pursuing a policy of unrestricted submarine warfare in retaliation to the blockade of Germany by the British Royal Navy. The Germans stated that, as part of this policy, they would attack any ship found within the war zone.
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