PrepTest 149, Section 4, Question 6
Astrophysicist: Gamma ray bursts (GRBs)—explosions of powerful radiation(54 more words not shown)
The conclusion of the astrophysicist's(13 more words not shown)
- ANo other GRBs(6 more words not shown)
- BThe classification of(11 more words not shown)
- CProperties other than(14 more words not shown)
- DGRBs cannot be(12 more words not shown)
- EDescriptive labels are(12 more words not shown)
Reading the argument
One oddball doesn't automatically make the categories useless.
'Long' and 'short' describe how long the bursts last. Apparently, those durations normally go with other properties too. This new burst breaks that pattern: it lasts a long time but otherwise resembles a short burst. We could acknowledge the exception and still find the usual labels helpful.
What we’re looking for
To support abandoning them, my first thought is a rule saying that an exception like this defeats the classification. That would give the author the strong connection the conclusion needs.
Working the answers
- A
If this is the only unusual case ever seen, the labels might have worked well in all the others. That doesn't establish that one exception makes them obsolete. A leaves our central objection in place instead of supplying a reason to abandon the classification.
- B
Being able to classify some bursts by duration alone makes duration sound useful in those cases. We need support for moving away from the duration-based labels. B doesn't explain why their usefulness has ended.
- CCorrect
The other properties matter more than duration in classifying this unusual burst. That gives us a reason not to let its long duration control the classification when its more important features match the short group. This takes a more specific route than my proposed rule about exceptions: it questions whether the labels emphasize the right feature. C supports reconsidering them without proving that duration is useless for every purpose.
- D
Ruling out classification by the events that create bursts doesn't show why classification by duration is inadequate. It removes another possible method without establishing the defect in the current one. We still need a reason this unusual burst makes 'long' and 'short' poor labels.
- E
How easily we can change the names doesn't tell us whether we should. We could rename a perfectly useful system Type I and Type II. The argument needs a problem with what the current labels convey, not merely the practical possibility of replacing them.
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