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#6 - The Rienzi, a passenger ship, sank as a result of a

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Complete Question Explanation

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 :arrow: 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.
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I chose B, the correct answer is C. I am really having difficulty with multiple sufficient and necessary conditions in a chain. Can someone please explain? Thanks
Nikki Siclunov
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Hi Cking14,

Thanks for your question. Here's how I would break down the conditional reasoning in the argument:

Sinking ship NOT fully flooded :arrow: Implode

Contrapositive: NOT implode :arrow: Sinking ship was fully flooded

Well, we know that the Rienzi sank, and that it didn't implode. By the contrapositive of the conditional statement in the second-to-last sentence, we know that the ship must have been fully flooded when it sank to the bottom.

Hopefully this puts you on the right track to figuring out why answer choice (C) is correct. As I'm sure you're aware, all questions in your Homework have been explained on the Online Student Center (Lesson and Homework Supplements/Lesson 3 Homework).

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Could you analyze the sentences and write out the diagram chain needed to solve the question? I do understand Rienzi did not implode, so it was fully flooded.

not fully flooded~~>implode

But the question needs more diagram to reach answer C and I can't figure out the correct diagram.

Thank you!
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The stimulus tells us that normally, a holed ship sinks too fast to flood all the way full - it doesn't fill up that quickly. It goes on to tell us that a sabotaged ship can, however, flood fully - that sets us sabotage as an alternative or exception to the normal situation, but not an exclusive one (there could still be a non-sabotage situation that it abnormal, right?)

So, if we know a ship flooded fully, we know that it was either a sabotaged ship or else it was, in some way, abnormal/unusual. We also know, as you correctly showed, that this ship was fully flooded. That means it has to have been either a) sabotaged or b) abnormal in some way. That's the set up for answer C - if one of those two things did not happen (sabotage), the other must have (abnormal/unusual).

If you wanted to diagram it conditionally, it might be something like Flood Fully (FF) -> S(abotage) or A(bnormal). The Sufficient Condition (FF) occurred, and if one of the two Necessary Conditions (S) did not, the other one (A) must have.

I hope that makes it clear. Keep up the good work!
Adam M. Tyson
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