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 Administrator
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#33165
Complete Question Explanation
(See the complete passage discussion here: lsat/viewtopic.php?t=13636)

The correct answer choice is (A)

Another Cannot Be True question, the correct answer to this one will be the one that cannot be true, based on the assumption that the passage’s statements about prions are accurate.

Answer choice (A): This is the correct answer choice. Prions are pathogens which, the author points out, lack nucleic acid and are instead composed mostly of protein. Since this choice presents the claim that nothing that lacks nucleic acid is a pathogen, it is clearly inaccurate and must therefore be the right answer to this Cannot Be True question.

Answer choice (B): The accuracy of this answer choice is confirmed by the author in the second paragraph, and this is a central point of the passage as well; this therefore cannot be the right answer to this Cannot Be True question.

Answer choice (C): The passage provides that a pathogen is a disease-causing agent, and that infections can only take place when the pathogenic agent is able to reproduce and create a viable presence in the organism. There is no implication that any pathogens exist that are unable to cause an infection. Since the choice is not refuted by the passage, it can be ruled out of contention in response to this Cannot Be True question.

Answer choice (D): In the final paragraph the author provides that it is now generally accepted that CJD is caused by prions, a new addition to the list of pathogens, confirming this choice to be accurate according to the passage. Since this question requires the choice that Cannot Be True, this choice must be ruled out.

Answer choice (E): The passage provides that prions are a fifth category of pathogenic agent, so the four pathogens listed are not the only ones. Since this choice passes the Fact Test, it cannot be the right answer to this Cannot Be True question.
 dandelionsroar
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#71837
Hi just a question on the setup of answer choice a, I get confused when a term like nothing starts of a sentence. Sometimes I translate it to a format that I find easier to digest, but I'm not sure if it's right. Can answer A be interpreted as 'no thing that doesn't have a nucleic acid is a pathogen', and then as 'a thing that doesn't have a nucleic acid is not a pathogen'? Can I just negate the necessary whenever I see a construction like this in the future?I

Thank you!!!
 Jeremy Press
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#71891
Hi dandelionsroar,

Yes, that's exactly the way to "translate" a phrase like that in answer choice A. We often use this example for "no" terms (including terms like "no," "no one," and "nothing"): No robots are humans. What does that mean? If something is a robot, then it is NOT a human. In essence, you're treating "no" (or "no one," or "nothing") as a sufficient condition indicator, and then transferring the negation to the second (the necessary) condition in the sentence.

The robot example would diagram as: Robot :arrow: NOT human.

Answer choice A would diagram as: Lack Nucleic Acid :arrow: NOT pathogen. That conditional relationship is clearly contradicted by the passage, where prions like that involved in CJD do not have nucleic acid, but are capable of reproducing and causing disease (and, hence, are pathogens).

I hope this helps!

Jeremy
 dandelionsroar
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#72097
very much so, thanks!

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