Which of these was a factor in the U.S. entry in World War I? A) the halt of the German army B) the sinking of the Lusitania C) the signing of a peace agreement D) the death of the heir to the Italian throneWhich of these was a factor in the U.S. entry in World War I? A) the halt of the German army B) the sinking of the Lusitania C) the signing of a peace agreement D) the death of the heir to the Italian throne'