QUESTION TYPE: Strengthen
CONCLUSION: Alzheimer’s may be caused by a virus.
REASONING: Blood from Alzheimer’s patients was injected into rats. The rats developed symptoms of Creutzfeld-Jacob disease, another degenerative neurological disorder. Creutzfeld-Jacob disease is caused by a virus.
ANALYSIS: The fact that the rats got sick implies that something in the human blood (perhaps a virus) caused them to get sick. But they got a different disease.
This doesn’t help show that Alzheimer’s is caused by a virus unless the two diseases are related. Answer choice D says they are the same disease.
- This would weaken the argument that Alzheimer’s is caused by a virus in humans.
- It doesn’t really matter what the symptoms are. The main point is that the disease is caused by a degeneration of brain tissue, just like Alzheimer’s.
- This also weakens the argument. We’d like to think that the disease is caused by a virus in both species.
- CORRECT. If the diseases aren’t the same then it isn’t clear how rats getting Creutzfeld-Jacob disease shows that Alzheimer’s is caused by a virus. Just because the diseases are both neurological disorders, that doesn’t mean they have the same causes.
- This doesn’t help much, because the sick rats were injected with human blood, not rat blood.
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