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# Manatees, aquatic mammals inhabiting Florida s rivers and

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Director
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Manatees, aquatic mammals inhabiting Florida s rivers and [#permalink]

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19 Feb 2009, 10:45
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Manatees, aquatic mammals inhabiting Florida’s rivers and coastal waters, swim close to the surface and are frequently killed in collisions with boats. To address the problem, boat traffic in manatee-populated waters is being required to maintain very low speeds. Unfortunately, manatees are unable to hear low-pitched sounds and a boat’s sound lowers in pitch as the boat slows. Therefore, this approach may in fact make things worse rather
than better.

Which of the following, if true, casts most doubt on the conclusion?
A. The areas where boats would have to maintain low speeds were decided partly on the basis of manatee-population estimates and partly from numbers of reported collisions between manatees and boats.
B. Because the water hyacinth that manatees feed on grows best in water that is nearly still, water hyacinth beds can be disturbed or damaged by fast-moving boat traffic.
C. Over the last several decades, boat traffic in Florida’s coastal waters has been increasing almost continuously and now represents the greatest threat to the endangered manatee population.
D. The sound of a boat engine generally travels much further under water than it does through the air.
E. When experimenters exposed manatees to the recorded sounds of boats moving at various speeds, the creatures were unable to discern the sounds over normal background noise.
Intern
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Re: CR: Manatees [#permalink]

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20 Feb 2009, 05:46
A, B and C are out of scope
E strengthening
D is the best
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Re: CR: Manatees [#permalink]

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20 Feb 2009, 15:23
E.
Current Student
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Re: CR: Manatees [#permalink]

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20 Feb 2009, 15:42
E.

As it says that the change in sound due to change in speeds is not noticeable by the Manatees. Hence slowing down the boats should not make matters worse.
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Re: CR: Manatees [#permalink]

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21 Feb 2009, 03:45
Confused b/s D and E. But E seems 2 b better choice.
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Re: CR: Manatees [#permalink]

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21 Feb 2009, 04:58
IMO E

should not be D becausethe argument says about pitch not the speed of sound
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Re: CR: Manatees [#permalink]

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21 Feb 2009, 12:05
OA E
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Re: CR: Manatees [#permalink]

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13 Mar 2010, 13:04
1
KUDOS
+1 for E
Re: CR: Manatees   [#permalink] 13 Mar 2010, 13:04
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# Manatees, aquatic mammals inhabiting Florida s rivers and

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