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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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27 Apr 2008, 12:05
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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.
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Director
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Re: CR: Manatees [#permalink]

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27 Apr 2008, 12:13
almost went with D..still thinking.
Director
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Re: CR: Manatees [#permalink]

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27 Apr 2008, 15:07
E. They are unable to discern the sounds, thus the conclusion is invalid.
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Re: CR: Manatees [#permalink]

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27 Apr 2008, 23:32
E.
prasannar wrote:
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.

Current Student
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Re: CR: Manatees [#permalink]

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28 Apr 2008, 17:22
E.

The conclusion claims that making boats slow down will make things worse. Since the manatees can't tell the difference between the sounds of slow boats, fast boats, or background noise, the number of manatee-boat collisions should remain the same regardless of boat speed.
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Re: CR: Manatees [#permalink]

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30 Apr 2008, 12:21
One more for E. As they cant distinguish sounds of boats traveling with different speed.
Whats the OA?
Manager
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Re: CR: Manatees [#permalink]

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30 Apr 2008, 12:33
prasannar wrote:
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.

I choose E.

I initially eliminated A, B, and C. I was hesitant on D. The conclusion revolves around manatees hearing boat engines under water and not how far engine noise can travel under water vs. air.
Manager
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Re: CR: Manatees [#permalink]

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30 Apr 2008, 13:16
E.

If the Manatees can not discern the difference between high and low boat speeds then it should not make the situation worse in this case.
Manager
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Re: CR: Manatees [#permalink]

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20 May 2008, 12:27
I feel B is right . We need to weeken the argument which states that 'slowing the boat will turn counter productive '.

B addresses the isssue.
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Re: CR: Manatees [#permalink]

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20 May 2008, 12:36
e is best..says the manatee cant tell the noise of a fast boat either..
Director
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Re: CR: Manatees [#permalink]

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08 Jun 2008, 21:03
Although I havent posted the question , the OA is E. I was to post the same question today,
Re: CR: Manatees   [#permalink] 08 Jun 2008, 21:03
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# Manatees, aquatic mammals inhabiting Florida s rivers and

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