PrepTest 105, Section 2, Question 4
An ingredient in marijuana known as THC has(34 more words not shown)
Which one of the following,(7 more words not shown)
- ASeveral teams of(13 more words not shown)
- BThe carcinogenic effect(12 more words not shown)
- CWhen THC kills(23 more words not shown)
- DIf chemists modify(14 more words not shown)
- ETo lessen the(21 more words not shown)
Reading the argument
Inactivating a virus sounds as though it might help. But the next fact changes that reaction: in these experiments, inactivated herpesviruses can turn healthy cells into cancer cells. That gives us a possible chain from THC to a harmful result.
Does that chain operate when someone uses marijuana? The experiments might involve conditions that don't carry over to that use. My main question is about the amount: how much virus does THC inactivate, and is that enough to produce the effect described?
Imagine the cancer-causing effect requires a large quantity of inactivated virus, while ordinary use produces only a tiny quantity. Those are hypothetical conditions, not established biological facts. They show the missing step between an experimental possibility and the conclusion about using marijuana.
What we’re looking for
For the weakener, I'd look for something disrupting that chain. My prediction concerns the amount involved, but another reason the experimental effect might not carry through would work too.
Working the answers
- A
Similar results from several research teams give us more reason to trust the experimental findings. That supports the evidence rather than challenging the move toward a cancer risk. It does not supply the weakener we need.
- BCorrect
This takes a different route from the amount prediction. THC is one ingredient in marijuana. If other ingredients neutralize its cancer-causing effect, the effect of THC by itself would not establish the effect of the whole mixture.
We could accept both experiments: THC inactivates the viruses, and inactivated viruses can cause the cell change. Yet the other ingredients could block the harmful effect when marijuana is used. That gives us a reason to doubt the conclusion without denying the findings. “Could be neutralized” weakens the proposed inference; it does not prove marijuana can never cause cancer.
- C
This actually gives another possible connection to cancer: a weakened immune system might have more trouble fighting viruses linked to cancers. So it is relevant, but it goes in the wrong direction. It adds a possible harmful mechanism rather than explaining why marijuana's use would avoid the effect at issue.
- D
Changing THC's chemical structure changes what we're discussing. A modified substance might be safe in a medication without showing that the original ingredient, as present in marijuana, is safe. The possibility of designing a different product doesn't undermine the argument about the existing one.
- E
A recommendation for cancer patients without the herpesvirus doesn't rule out a risk involving that virus. A product can also be recommended for one benefit while carrying other risks. This answer doesn't show that the chain described in the argument fails in people who do have the relevant virus.
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