(A) War Declaration
(B) Unrestricted warfare
(C) ** The Sussex Pledge
(D) The Treaty of Versailles
EXPLANATIONS BELOW
Concept note-1: -The attack prompted a U.S. threat to sever diplomatic relations. The German government responded with the so-called Sussex pledge (May 4, 1916), agreeing to give adequate warning before sinking merchant and passenger ships and to provide for the safety of passengers and crew.
Concept note-2: -…the adoption of the so-called Sussex pledge (May 4, 1916), which obliged German submarine captains to precede the torpedoing of merchant or passenger ships with a warning and to provide for the safety of passengers and crew of sunken ships in the wake of such attacks.
Concept note-3: -The disaster set off a chain of events that led to the U.S. entering World War I. A German U-boat torpedoed the British-owned steamship Lusitania, killing 1, 195 people including 128 Americans, on May 7, 1915. The disaster set off a chain of events that led to the U.S. entering World War I.
Concept note-4: -The Lusitania Sinks: May 7, 1915 The United States eventually protested the action, and Germany apologized and pledged to end unrestricted submarine warfare.