An arco book arco is a registered trademark of Thomson Learning, Inc., and is used herein under license by Peterson’s. About The Thomson Corporation and Peterson’s

62. The correct answer is (B). World War I was precipitated by the assassination of the Austrian Arch-
duke at Sarajevo in 1914, but the United States did not immediately enter the war. Although most
Americans tended to sympathize with Great Britain and to distrust Germany, the express policy of the
United States government was neutrality. Gradually, however, the events of the war, amplified by
British propaganda, polarized the Americans, and most favored the British. The immediate cause for
U.S. entry into the war was German submarine warfare. In 1915, hoping to stop supplies coming
from Britain, Germany announced that it would thenceforth consider the waters surrounding the
British Isles a war zone and warned neutral ships to stay clear. The main weapon for enforcing the
blockade was the submarine. In 1915, a German U boat (for unterseeboot) torpedoed and sank the
British passenger liner Lusitania. Over a hundred American passengers were lost. After strong protest
by the United States, the German government promised that it would sink no more passenger ships.
But in March 1916, a German submarine mistakenly sank the ferry Sussex in the English Channel.
This time the German government responded with the Sussex Pledge promising that it would not attack
merchant vessels without warning. This move reduced tensions with the United States but also permit-
ted supplies to reach the Allied forces in Europe. In 1916, Wilson’s supporters coined the slogan “He
kept us out of war.” But in early 1917, Germany decided that it could not win the war without enforcing
the blockade and announced the resumption of unrestricted submarine warfare. Several American mer-
chant ships were sunk. In February, the British intercepted a message from the German foreign secre-
tary, Alfred Zimmerman, to the German ambassador in Mexico, instructing the ambassador to offer
Mexico a military alliance against the United States with the promise it would help Mexico recover lost
territory. On April 2, President Wilson asked Congress for a declaration of war.