The cause of the wreck of the ship Edmund Fitzgeraid in a severe storm on lake Superior is still unknown , when the sunken wreckage of the vessel was found , searchers discovered the hull in two pieces lying close together , The storm' s violent waves would have caused separate pieces floating even briefly on the surface to drift apart. Ttherefore, the breakup of the hull can be ruled out as the cause of the sinking. Which of the following is an assumption on which the argument depends? ['If the ship broke up before sinking , the pieces of the hull would not have remained on the surface for very long', 'Under water currents at the time of the storm did not move the separated pieces of the hull together again .', 'Ships as large as the Edmund Fitzgerald rarely sink except in the most violent weather.', 'Pieces of the hull would have sunk more quickly than the intact hull would have']