Answer:
B. major battles and outcomes
Step-by-step explanation:
World War II was a global conflict that resulted in military action taking place against different countries that lasted between 1939 and 1945.
This war was launched against Nazi Germany and most nations of the world were involved and were grouped along the lines of allies or enemies. This war is described as the greatest battle in history because of the sheer number of nations and soldiers involved and how its outcome shaped the world forever.
This period marked the death of both military personnel and civilians because of the airstrikes, raids, missiles, etc that were in use which claimed about 65 million lives in just under 6 years.
Therefore, the most effective organizing principle for writing the history of World War II would be major battles and outcomes.