President woodrow wilson was reelected in 1916 with the of the slogan “he kept us out of war”. the next year, however, he led the united states into the war on the side of the allies. which of the following events contributed to american involvement in the war?
a) russia entering the war in 1917
b) the sinking in 1915 of the british liner lusitania
c) the halt of unrestricted german submarine warfare in 1917
d) a german attempt to turn canada against the united states