PrepTest 106, Section 1, Question 26
Modern navigation systems, which are found in most(88 more words not shown)
Which one of the following,(7 more words not shown)
- AAfter the laptop(17 more words not shown)
- BWhen in use(13 more words not shown)
- CNo problems with(17 more words not shown)
- DSignificant electromagnetic radiation(26 more words not shown)
- EPlanes were first(14 more words not shown)
Reading the argument
The laptop came on, and the plane went off course. Was the laptop responsible, or was that a coincidence?
The background makes the concern understandable. These navigation systems are more susceptible to interference, and they use radio signals during landing. Still, the timing of one incident doesn't establish what caused it. Something else could have affected the navigation system just as the passenger switched on the laptop.
At first, I also wonder why aircraft use the more vulnerable circuitry. Perhaps it has benefits that offset that drawback. But the author's conclusion isn't that the older circuitry is better overall. The claim is that passengers' electronic devices put the modern systems at risk. That's the connection we need to test.
What we’re looking for
The question asks which fact least strengthens the argument. Four choices should help support that connection, leaving one that does less—or nothing—to help. I'd look for whether each choice gives us a reason to attribute the problem to the devices, rather than just repeating that the events happened together.
Working the answers
- A
This adds a useful second part to the sequence. Laptop on: the navigation problem appears. Laptop off: the system returns to normal. That doesn't rule out every coincidence, but it makes the proposed connection more convincing than the original single observation. A strengthens the argument.
- B
This provides a mechanism. The devices emit electromagnetic radiation, and that radiation is known to interfere with circuitry. Now we have a reason a passenger's device could affect a navigation system, rather than merely a record of two events occurring at the same time. B strengthens.
- C
Flights without passenger-owned devices have no reported problems with the navigation equipment or dials. That comparison fits the suspicion that the devices contribute to the problems: when the suspected source is absent, the reported problem is absent too.
It doesn't prove that the devices caused every problem elsewhere, and “not reported” doesn't establish that no problem ever occurred. But it does supply additional support, so C isn't the least helpful choice.
- D
This helps establish that the interference could reach the relevant equipment. The radiation can travel up to eight meters, while some seats are within four meters of the navigation systems. Passengers can therefore sit within the stated range.
That doesn't show that every device disrupts every flight. It does answer a practical question about the proposed mechanism: the source of interference can be close enough to reach the system. D strengthens.
- ECorrect
Two technologies becoming common around the same time doesn't tell us that one interferes with the other. E gives us a historical coincidence, not a connection between a device's use and a navigation problem.
Compare what is missing: no change when a device is switched off, no mechanism, no flights-without-devices comparison, and no evidence that the interference can reach the equipment. E doesn't even say navigation problems increased when portable devices became popular. It is the least helpful support for the claimed risk.
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