Which of the Following Is Among the Reasons the Great

Which of the following is among the reasons the Great War was especially challenging?

A) The war would cause more destruction and involve more nations than any previous conflict.
B) The war coincided with a highly public and controversial divorce from Wilson's wife Ellen.
C) Wilson had plotted to topple several European monarchs, but all remained in power after the war.
D) Actions taken by the United States had been the primary cause of the start of the war.
E) Great Britain had been a latecomer to industrialization but was the main American ally.