Read the quotation from President Woodrow Wilson's speech to Congress on April 2, 1917 and answer the question.


The new policy has swept every restriction aside. Vessels of every kind, whatever their flag, their character, their cargo, their destination, their errand, have been ruthlessly sent to the bottom without warning and without thought of help or mercy for those on board, the vessels of friendly neutrals along with those of belligerents.


In this quotation, President Wilson acknowledged the need for a change in US policy. What caused this policy shift?


A.

Germany began launching attacks on British civilian targets.


B.

Germany attacked US military vessels sailing in European waters.


C.

Germany invaded the neutral nation of Belgium during a war.


D.

Germany instituted a policy of unrestricted submarine warfare.