The main reason for the passage of the National Security Act was to separate the armed forces into different departments. enable the nation to meet the challenges of the Cold War. prevent labor unions from striking during times of war. desegregate each branch of the nation's armed forces.

Well the the answer is most likely to be enable the nation to meet the challenges of the cold war

Under the national Security Act, the navy, the army, and the air force were unified into one centralized structure so it eliminated option A and D.

as for option C, Labor union is not the largest worry of the U. S Government during the time, i think it's not the answer (The Act was created during the cold war era)