PrepTest 109, Section 1, Question 25
The number of airplanes equipped with a new(60 more words not shown)
Which one of the following,(7 more words not shown)
- AThe new anticollision(10 more words not shown)
- BIt was not(17 more words not shown)
- CThe new anticollision(17 more words not shown)
- DKey information began(14 more words not shown)
- EThe sudden disappearance(13 more words not shown)
Reading the argument
A device that helps planes avoid collisions sounds useful. But the passage raises a different question: could it also interfere with the information air traffic controllers receive?
More planes acquired the device while information losses became more common. The shared frequency gives us a plausible reason to suspect interference. Still, those facts don't settle what caused the missing information. What else changed during those two years? Perhaps the computer systems or communication connections developed problems. Those are possibilities to investigate, not facts we've established.
What we’re looking for
For a weakener, I'd expect evidence of another cause, or evidence that clears the device of this particular effect. We don't have to deny that information disappeared. We need to challenge the explanation for why it disappeared.
Working the answers
- A
A device can work as intended and have an unwanted side effect. Preventing collisions doesn't show that it leaves the controllers' information unaffected. A supports the device's usefulness, but that isn't the claim we're evaluating.
- B
This helps the author's timing story: the problem didn't start until the device was introduced. That doesn't prove the device caused it, because something else could have changed too. But it makes the proposed sequence more plausible rather than challenging it. We need the opposite direction.
- C
Moving the device to another frequency might be a sensible response if interference is the problem. But a scheduled change is not evidence that the current device does or doesn't cause the information losses. We aren't told what happens to the losses after the change. A planned solution doesn't establish the cause of the problem.
- DCorrect
This attacks the timing rather than identifying a specific alternative cause. The information was disappearing three months before the device was even tested. How could that device have caused the earlier losses?
Something else must account for those earlier incidents. That makes the author's explanation of the phenomenon less convincing: seeing the device and the problem become more common together doesn't establish that the device produced the problem.
D doesn't prove that the device could never contribute to later losses. It doesn't need to. It gives us evidence that this problem already existed without the proposed cause, which weakens the attribution.
- E
Why would airport size decide whether the device is responsible? We'd need more information connecting size with the devices, the radar systems or another possible cause. Perhaps large airports have more equipped planes; perhaps they have some separate problem. E gives a pattern without the link that would make it count against the author's explanation.
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