Answer:
D >> 40 million casualties
Step-by-step explanation:
Total casualties from all sides and fronts—including war's civilian losses—approximately 41 million. 23 million injured, 18 million killed. Between 9 and 11 million soldiers have died in battle; other accounts put the number at 12 million. Of those, around half are missing and assumed dead. Artillery fire instantly obliterated a large number of troops. Some nations are difficult to obtain accurate statistics from. During World War II, some nations preserved weak archives, some destroyed their records, and some just disappeared. However, we do have the rough estimates above.