That the policy of nuclear deterrence has worked thus far is unquestionable. Since the end of the Second World War, the very fact that there were nuclear armaments in existence has kept major powers from using nuclear weapons, for fear of starting a worldwide nuclear exchange that would make the land of the power initiating it uninhabitable. The proof is that a third world war between superpowers has not happened. Which one of the following, if true, indicates a flaw in the argument? ['Continuing to produce nuclear weapons beyond the minimum needed for deterrence increases the likelihood of a nuclear accident.', 'The major powers have engaged in many smaller-scale military operations since the end of the Second World War, while refraining from a nuclear confrontation.', "Maintaining a high level of nuclear armaments represents a significant drain on a country's economy.", 'It cannot be known whether it was nuclear deterrence that worked, or some other factor, such as a recognition of the economic value of remaining at peace.']