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# Manatees, aquatic mammals inhabiting Florida s rivers and

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

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19 Jun 2010, 09:25
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75% (hard)

Question Stats:

57% (02:13) correct 43% (01:35) wrong based on 863 sessions

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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 normalbackground noise.

I marked the OA by PoE, but I was not much clear on the argument. Can someone explain on the argument and answer choice?
[Reveal] Spoiler: OA

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Last edited by RaviChandra on 12 Aug 2015, 21:30, edited 2 times in total.
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Re: Manatees, aquatic mammals inhabiting Florida s rivers and [#permalink]

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20 Jun 2010, 11:10
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I think the answer is E.

The hypothesis is that boats traveling slow = less manatees killed. However, manatees can't hear slow boats and therefore, slow boats will make the problem WORSE. The argument is saying that boats traveling at various speeds will kill less manatees than all boats traveling slowly on the account that manatees can't hear slow boats.

To cast doubt on this, we can show that manatees can't hear various speeds. Thus, mandating slow boats will not make the problem WORSE, it should stay the same.
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Re: Manatees, aquatic mammals inhabiting Florida s rivers and [#permalink]

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26 Jul 2010, 02:37
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E.
Seemed easy to me.

because boats drive fast they kill manatee.
Why? there are two reasons: either manatees are sluggish or deaf.
conclusion: author says that deafness kills M. we must introduce evidence that would make author to reconsider his her conclusion by saying "ohh... I am stupid I did not account for this"

E says that M can't discern sounds, so they die not due to deafness, but becuase they are sluggish.
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Re: Manatees, aquatic mammals inhabiting Florida s rivers and [#permalink]

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06 Feb 2014, 19:26
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Conclusion: Therefore, this approach may in fact make things worse rather than better.

Reasoning: High boat speeds kills manatees. Slow boat speeds kills more manatees because manatees cannot hear any sound. To weaken the argument, the statement must provide that slow boat speeds do not kill any more than high boat speeds. (Wrong answers are neutral or provide reasons why slow boat speeds do kill more manatees than high boat speeds.)

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. Neutral. Statement does not cast doubt.

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.Wrong. Statement provides a reason why more manatees are present in waters with slow boat speeds.

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. Neutral. More boats kill more manatees; nothing about boat speeds.

D. The sound of a boat engine generally travels much further under water than it does through the air. Opposite answer - admittedly, this one threw me off. I forgot if this question were a strengthen or weaken, and key words such as "engine" + "travel much further" made a good trap. Brain fail.

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. OK - that slow boat speeds do not kill any more than high boat speeds.
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Re: Manatees, aquatic mammals inhabiting Florida s rivers and [#permalink]

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20 Jun 2010, 07:43
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IMO B
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Re: Manatees, aquatic mammals inhabiting Florida s rivers and [#permalink]

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21 Jun 2010, 00:43
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Now I am hesitant on B. But the only contenders are B / E.

E is only one which DELINKS the speed of boat as the key force of the argument.
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Re: Manatees, aquatic mammals inhabiting Florida s rivers and [#permalink]

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20 Jun 2010, 07:53
D
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Re: Manatees, aquatic mammals inhabiting Florida s rivers and [#permalink]

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20 Jun 2010, 11:26
IMO B.
water hyacinth beds can be disturbed or damaged by fast-moving boat
traffic. when Boats maintain low speeds, it cant worsen things.

OA?
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Re: Manatees, aquatic mammals inhabiting Florida s rivers and [#permalink]

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20 Jun 2010, 22:00
Yes B.

Apply negation on B. And arg will reverse.
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Re: Manatees, aquatic mammals inhabiting Florida s rivers and [#permalink]

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20 Jun 2010, 23:36
E...if they cannot distinguish different boat sounds, there won't be much difference (the situation will maybe improve), and the conclusion is weakened...
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Re: Manatees, aquatic mammals inhabiting Florida s rivers and [#permalink]

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21 Jun 2010, 01:50
E IMO We are supposed to logically negate the argument. E does that by making the stituation from worse ------ > Same .

QA plz ?
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Re: Manatees, aquatic mammals inhabiting Florida s rivers and [#permalink]

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21 Jun 2010, 09:11
I believe the answer should be E. B though mentions that fast boats can kill the manatees, but no where it mentions if the slow boats are going to help and reduce the collisions.

B answer choice is like a Shell game.

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

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21 Jun 2010, 10:13
What is a shell game? How is it affecting the argument?

amp0201 wrote:
I believe the answer should be E. B though mentions that fast boats can kill the manatees, but no where it mentions if the slow boats are going to help and reduce the collisions.

B answer choice is like a Shell game.

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

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21 Jun 2010, 14:02
Shell game is like the answer choice most similar to correct one, though not the correct one.

The argument's conclusion is - slower boats might worsen the problem.

Answer choice E says Manatees are not able to hear noises at any levels. Hence the problem won't worsen but will stay same.

Hence I believe to be E rather than B. Thank You.

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

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22 Jun 2010, 03:17
E
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Re: Manatees, aquatic mammals inhabiting Florida s rivers and [#permalink]

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22 Jun 2010, 11:47
E ?
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Re: Manatees, aquatic mammals inhabiting Florida s rivers and [#permalink]

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22 Jun 2010, 12:29
OA is E. Good catch by krypt.
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Re: Manatees, aquatic mammals inhabiting Florida s rivers and [#permalink]

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22 Jun 2010, 21:17
krypt wrote:
I think the answer is E.

The hypothesis is that boats traveling slow = less manatees killed. However, manatees can't hear slow boats and therefore, slow boats will make the problem WORSE. The argument is saying that boats traveling at various speeds will kill less manatees than all boats traveling slowly on the account that manatees can't hear slow boats.

To cast doubt on this, we can show that manatees can't hear various speeds. Thus, mandating slow boats will not make the problem WORSE, it should stay the same.

what's the background sound means here; They'll not be able to distinguish b/w Boat noise and normal noise?
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Re: Manatees, aquatic mammals inhabiting Florida s rivers and [#permalink]

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26 Jul 2010, 04:26
on reverification got E as correct
wasted approx 6 min
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Re: Manatees, aquatic mammals inhabiting Florida s rivers and [#permalink]

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26 Jul 2010, 21:54
i also thought B
but E it shud be
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Re: Manatees, aquatic mammals inhabiting Florida s rivers and   [#permalink] 26 Jul 2010, 21:54

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