The initial causes of serious accidents at nuclear power plants have not so far been flaws in the advanced-technology portion of the plants. Rather, the initial causes have been attributed to human error, as when a worker at the Browns Mills reactor in the United States dropped a candle and started a fire, or to flaws in the plumbing, exemplified in a recent incident in Japan. Such everyday events cannot be thought unlikely to occur over the long run. Which one of the following is most strongly supported by the statements above? ['No serious accident will be caused in the future by some flaw in the advanced-technology portion of a nuclear power plant.', 'Now that nuclear power generation has become a part of everyday life, an ever-increasing yearly incidence of serious accidents at the plants can be expected.', 'The design of nuclear power plants attempts to compensate for possible failures of the materials used in their construction.', 'If nuclear power plants continue in operation, a serious accident at such a plant is not improbable.']