Must Be True. The correct answer choice is (D)
In bad weather (when visibility is poor), the airport cannot land planes on adjacent runways at the
same time, because the runways are too close to one another. This reduces the maximum number of
planes that the airport can land each hour, from 60 in good weather, to 30 in bad weather. Schedules
assume good weather, the author provides, so bad weather causes big delays.
- Premise: Bad weather reduces the maximum number of planes per hour, from 60 to 30.
Premise: Airline schedules assume good weather.
Conclusion: Bad weather causes major delays.
the airport? Bad weather, as we know, can cause major delays; reducing the number of planes that
can land, from 60 to 30, causes these delays, so it must be that 30 planes per hour is not enough to
keep things at this airport running smoothly.
The question that follows is a Must Be True question, so the correct answer choice must pass the
Fact Test: Only the right answer choice will be able to be confirmed by the information provided in
Answer choice (A): This answer choice claims that each runway can only land half as many planes
in bad weather as in good. Based on the information provided in the stimulus, the issue with bad
weather is that only one of two runways can be used in poor visibility—that is why bad weather
leads to delays. This clever wrong answer caught many test takers, because the stimulus provides
that the number of planes that can possibly land on the two runways together is cut in half, but that
does not necessarily mean that the capacity of each individual runway is cut in half. This choice
cannot be confirmed by the stimulus, so it cannot be the correct answer choice.
Answer choice (B): The stimulus provides that good weather allows for adjacent runways to be used
simultaneously, but that does not dictate that planes are landing constantly on both. Since this choice
is not confirmed by the information in the stimulus, it fails the Fact Test and should be ruled out of
Answer choice (C): This choice claims that serious delays result from simultaneous use of two
runways—but according to the stimulus, the delays come about when planes are unable to land
simultaneously. Thus, this choice is something of an Opposite answer.
Answer choice (D): This is the correct answer choice. If, as the author of the stimulus provides,
the 30 plane per hour limitation is too much, and thus leads to delays, it must be that more than 30
planes per hour are normally scheduled.
Answer choice (E): The information provided by the author is limited to what happens in bad
weather (major delays). Since no information is provided regarding the airport’s normal operations,
this choice cannot be confirmed by the information in the stimulus, fails the Fact Test, and should be
ruled out of contention.