The Rienzi, a passenger ship, sank as a result of a hole in its hull, possibly caused by sabotage. Normally, when a holed ship sinks as rapidly as the Rienzi did, water does not enter the ship quickly enough for the ship to be fully flooded when it reaches the ocean floor. Full flooding can be achieved, however, by sabotage. Any ship that sinks deep into the ocean when not fully flooded will implode. Deep-sea photographs, taken of the sunken Rienzi where it rests on the ocean floor, reveal that the Rienzi did not implode. Which one of the following must be true on the basis of the information above? ['If the Rienzi was not sunk by sabotage, water flooded into it unusually fast.', 'The Rienzi was so strongly constructed as to resist imploding under deep-sea pressure.', 'If the Rienzi had sunk more slowly, it would have imploded.', 'If the Rienzi became fully flooded, it did so only after it reached the ocean floor.']