Answer: The Answer is option D
Explanation: Combat training was the key aspect for the American military in preparing the ten million American men for World War II. As the United States entered the war, there was a massive mobilization effort to train and equip millions of men to fight in the war. The military placed a strong emphasis on combat training, as it was essential for soldiers to be well-prepared for the challenges they would face on the battlefield. Combat training included basic training, which covered the fundamentals of military tactics, discipline, and physical conditioning, as well as more advanced training in specialized areas such as infantry, artillery, and aviation. By providing extensive combat training to its soldiers, the American military aimed to ensure that they were ready to face the challenges of war and protect the nation's interests.