What qualities led to america’s exceptional success as a democratic government?

d. the right to establish a one-house legislature

i am not 100   percent sure but i do know that hitler was burned to death with gas so that makes me think it is d. because they were under his control if they fail or not do as told they will be killed but i could be wrong hope this

the missile gap was the cold war term used in the us for the perceived superiority of the number and power of the ussr's missiles in comparison with its own (a lack of military parity).