The correct answer is A. Americans were aboard the British passenger ship when it went down.
The sinking of the RMS Lusitania on May 7, 1915, upset many Americans primarily because there were 128 American passengers among the 1,198 victims. The incident fueled anti-German sentiment in the United States and played a significant role in the growing push toward U.S. involvement in World War I. While there were other factors at play, such as the nature of unrestricted submarine warfare and Germany's prior pledges, the loss of American lives was a critical factor in the public outcry.