Why Was World War I Called a "Total War

Why was World War I called a "total war"?

A) All of the countries in Europe, their colonial possessions, and the United States were involved in it.
B) The entire industrial capacity of participating states and all civilian and military personnel were mobilized to fight the war.
C) The new weapons of war, including poison gas and machine guns, killed virtually everyone in their path.
D) Armies on both sides used a scorched-earth tactic to destroy all crops, livestock, buildings, and infrastructure in their paths.