PrepTest 149, Section 4, Question 4
It has been hypothesized that our solar system(64 more words not shown)
Which one of the following(7 more words not shown)
- AIf a meteorite(26 more words not shown)
- BOther solar systems(12 more words not shown)
- CSupernovas do not(11 more words not shown)
- DResearchers have found(13 more words not shown)
- EIf there had(24 more words not shown)
Reading the argument
What if we're looking in the wrong place? Iron-60 could have been present early in the solar system without ending up in the meteorites the researchers examined. Perhaps it was elsewhere, such as deep inside planets.
And even if it once reached those meteorites, would it still be detectable now? Imagine it breaking down over time. That's another possible reason an ancient substance might not appear in a present search. These are possibilities to test, not claims about what iron-60 actually does.
What we’re looking for
We can accept that a supernova origin would have put iron-60 in the early solar system. But finding none in old meteorites doesn't establish that none was present anywhere. For the required assumption, I'd look for a connection answering one of those concerns: if the iron was there, this search should reveal it.
Working the answers
- A
The presence of other chemical elements unlikely to come from a supernova doesn't establish where iron-60 would be found. The argument relies on the absence of one expected substance, not on detecting some different substance with a different origin. It doesn't require A's description of early meteorites.
- B
How other solar systems formed is outside this argument. This solar system could fail to have a supernova origin even if another system did have one. The author needs a reliable way to test our system's proposed history, not a universal rule about every system.
- C
A supernova could produce several kinds of iron while still producing iron-60. Other forms wouldn't erase the expectation that iron-60 was initially present under the hypothesis. The argument doesn't need iron-60 to be the only significant form produced.
- D
We don't need a later discovery of iron-60 to argue from its absence in the early meteorites. Perhaps researchers have never found it in any meteorite. D gives a result from a different period, without supplying the needed link between early presence and the objects examined.
- ECorrect
If iron-60 had been present early, it would be found in these early meteorites. That is the connection needed to treat the failure to find it as evidence that it wasn't there. Without it, the substance could have existed somewhere the search didn't cover or in a form no longer detectable. E rules out the possibility that the hypothesized early presence would leave no findable iron-60 in the relevant meteorites.
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