Must Be True-SN. The correct answer choice is (C)
The key to answering this question quickly and efficiently is to focus solely on those facts that can be put together to form a logically valid inference. For instance, you should notice the strong element of conditionality between full flooding and implosion: any sinking ship that is not fully flooded will implode:
- Fully flooded Implode
According to the last sentence in the stimulus, the Rienzi apparently did not implode. By the contrapositive of the above-mentioned statement, the Rienzi must have been fully flooded when it sank to the bottom of the ocean.
While the author observes that full flooding can be achieved by sabotage, the relationship between the two is not conditional but causal (the author only states that full flooding "can be achieved by sabotage," not that it necessarily "must" be achieved by sabotage). Therefore, we can only conclude that sabotage was a likely cause for the full flooding, a possibility that is also supported by the first sentence in the stimulus. If sabotage was not the cause, however, water must have flooded the ship unusually fast, since under normal circumstances it does not enter the ship quickly enough to fully flood it before the ship sinks to the bottom of the ocean.
Answer choice (A): It is entirely possible that the Rienzi sunk by impact, which caused the water to flood the ship unusually fast. How the ship was constructed is irrelevant and not inferable from the evidence presented in the stimulus.
Answer choice (B): This answer choice is directly disproven by the information in the stimulus, since any ship that sinks deep into the ocean floor when not fully flooded will implode, and the Rienzi did not implode. Therefore, the Rienzi must have been fully flooded when it reached the ocean floor.
Answer choice (C): This is the correct answer choice. Indeed, if sabotage was not the reason why the Rienzi was fully flooded and water cannot enter the ship quickly enough, water must have flooded into it unusually fast. See discussion above.
Answer choice (D): There is no reason to suspect that had the Rienzi sunk more slowly, it would not have imploded. The stimulus contains no evidence to suggest that the speed at which ships sink has any effect on whether they implode or not. Furthermore, even if a slower sinking ship has a higher chance of being fully flooded when it reaches the bottom of the ocean, such a ship can still implode. To conclude otherwise would be to rely on the Mistaken Negation of the conditional relationship between flooding and imploding.
Answer choice (E): How the ship was built is immaterial to the information provided in the stimulus: the fact remains that any ship that sinks deep into the ocean when not fully flooded will implode. This answer choice is incorrect.