DISCUSSION: A pathogen is something that causes diseases and replicates itself (see first sentence of 1st paragraph). Prions appear to be pathogens (see last two sentences of 2nd paragraph).
We used to think that pathogens had DNA, but prions lack DNA (see third-to-last line of 2nd paragraph).
This question asks us to assume that all the facts we learned about prions are true. Remember, we’re looking for things that must be false. It’s possible that certain answers could be false, but that’s not enough. B and C aren’t necessarily true, for instance, but they could be true, and that’s all you need.
- CORRECT. The contrapositive of this answer is: pathogens have nucleic acid. But the theory says that prions are pathogens and that they lack nucleic acid (third-to-last line of 2nd paragraph). So this answer contradicts the passage.
- This seems true. The passage implies that the discovery of prions was recent.
- The first three lines of 1st paragraph support this. Pathogens are things that cause disease.
- If the prion theory is correct, then prions are pathogens, and prions cause CJD. So this answer would be true.
- This seems true. If the prion theory is correct, then prions are also pathogens. Prions are not bacteria, viruses, fungi or parasites.
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