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# Manatees, aquatic mammals inhabiting Florida s rivers and

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Manager
Joined: 01 Aug 2007
Posts: 73

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

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06 Oct 2007, 19:46
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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.
23
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.

Kudos [?]: 18 [0], given: 0

VP
Joined: 10 Jun 2007
Posts: 1434

Kudos [?]: 370 [0], given: 0

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06 Oct 2007, 21:23
younggun044 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.
23
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.

E. Since manatees cannot hear the sound anyways, slowing speed will not make things worse.
B comes close, but it talks about what manatee eats will be better. However, the argument here is addressing collision, not the food. So this is irrelevant.
A,C,D are all irrelevant.

Kudos [?]: 370 [0], given: 0

Manager
Joined: 07 Aug 2005
Posts: 124

Kudos [?]: 2 [0], given: 0

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06 Oct 2007, 21:35
younggun044 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.
23
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.

Between B, D and E, I pick E.
manatees can not distinguish the sound of boats moving at various speed, so reduced speed of boat will not make things worse.

Kudos [?]: 2 [0], given: 0

Director
Joined: 18 Jul 2006
Posts: 523

Kudos [?]: 71 [0], given: 0

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06 Oct 2007, 23:29
Only E makes sense.

Kudos [?]: 71 [0], given: 0

Manager
Joined: 01 Aug 2007
Posts: 73

Kudos [?]: 18 [0], given: 0

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07 Oct 2007, 00:34
younggun044 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.
23
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.

You ppl are good.
OA is E.

Kudos [?]: 18 [0], given: 0

SVP
Joined: 28 Dec 2005
Posts: 1543

Kudos [?]: 185 [0], given: 2

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07 Oct 2007, 07:16
Yup its gotta be E.

If manatees cant distinguish the low noise from a boat motor from that of just normal background noise, they'll still come to the surface

Kudos [?]: 185 [0], given: 2

CEO
Joined: 29 Mar 2007
Posts: 2553

Kudos [?]: 528 [0], given: 0

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07 Oct 2007, 11:28
younggun044 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.
23
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.

Took me a bit to get this one, cause i didn't like any of the answers.

E it is. E says that Manatees didn't hear any difference in pitch whether the boat was going faster or not. So this weakens the conclusion.

Kudos [?]: 528 [0], given: 0

Senior Manager
Joined: 16 Apr 2006
Posts: 270

Kudos [?]: 242 [0], given: 2

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07 Oct 2007, 12:47
I will go for E but initially I thought it's A.
_________________

Trying hard to achieve something unachievable now....

Kudos [?]: 242 [0], given: 2

07 Oct 2007, 12:47
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# Manatees, aquatic mammals inhabiting Florida s rivers and

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