DISCUSSION: On this type of question, narrow it down to 1-2 answers, then check the passage for confirmation. You can almost always prove a ‘most strongly supported’ question by reference to the passage.
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- CORRECT. The last sentence of 1st paragraph says that scientists traditionally believed that pathogens had DNA. The rest of the passage says that prions are a pathogen that has no DNA yet causes CJD.
- The passage never mentions how CJD spreads or if prions are contagious. The passage implies that prions aren’t contagious, because they are produced within our body (second-to-last sentence of 4th paragraph). That’s why our immune systems don’t attack them.
If your prions entered someone else’s body, their immune system would likely react. You can use outside knowledge to make warranted assumptions: we know immune systems often reject foreign tissues. - Unfortunately, we don’t really understand why prions reproduce and cause disease (last sentence of 4th paragraph), so we don’t know how to stop CJD.
- The last sentence of 3rd paragraph directly contradicts this answer. There are wide variations in how the disease progresses.
- The first sentence of 4th paragraph makes clear that the prion theory of CJD now has considerable support. There was only initial skepticism.
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