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The dwarf masked owl, a rare migratory bird of prey, normally makes it

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The dwarf masked owl, a rare migratory bird of prey, normally makes it [#permalink]

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The dwarf masked owl, a rare migratory bird of prey, normally makes its winter home on the Baja peninsula, where it nests in the spiny cactus. In fact, there are no other suitable nesting sites for the dwarf masked owl on the Baja peninsula. But a blight last spring destroyed all of the spiny cacti on the Baja peninsula. So unless steps are taken to reestablish the spiny cactus population, the dwarf masked owl will not make its home on the Baja peninsula this winter.

The argument depends on assuming which one of the following?

(A) No birds of prey other than the dwarf masked owl nest in the spiny cactus.

(B) If the Baja peninsula contains spiny cacti, then the dwarf masked owl makes its winter home there.

(C) On occasion the dwarf masked owl has been known to make its winter home far from its normal migratory route.

(D) The dwarf masked owl will not make its winter home on the Baja peninsula only if that region contains no spiny cacti.

(E) Suitable nesting sites must be present where the dwarf masked owl makes its winter home.
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Re: The dwarf masked owl, a rare migratory bird of prey, normally makes it [#permalink]

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New post 16 Mar 2017, 12:51
yogesh610 wrote:
i marked the answer to be D..explanations please?????


In the question stem, the conclusion is that if we don't re-establish the cactus population, the Owl will not make its home in Baja. So we need something in the answer choices which supports this conclusion. Also note that the stem tells us that without the spiny cacti, there will be no nesting sights in Baja (because it states that there are no other nesting sites in Baja).

Choice "D" tells you that if it didn't make it's home in Baja, then the reason must be that there were no spiny cacti (and no other reason).

But this doesn't exclude that the Owl still makes its home in Baja, despite there being no spiny cacti! All we know from the stem is that in order to have nests, the owl needs spiny cacti - maybe the owl still just wants to chill in Baja without nests! I heard it is a nice area, after all.

The missing link is choice "E", which links the fact that there will be no nests to our conclusion - that the owl won't make its home in Baja.

A similar example: The party is out of pizza. Unless we get more pizza, Craig won't come to the party.
(the assumption is clearly that without pizza, Craig won't come to the party)

...
...
...
D) Craig will not come to the party only if there is no pizza. (i.e. If Craig doesn't come to the party, the only possible reason is because there is no pizza. This doesn't rule out me coming, even if there is no pizza, it only tells you that if I don't show up, you know the reason.)

E) Craig will not come to a party without pizza (another way to say this - if there is no pizza, Craig won't come to the party).

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Re: The dwarf masked owl, a rare migratory bird of prey, normally makes it [#permalink]

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New post 19 Mar 2017, 01:46
hii , expert although i got the right answer for this and understood the above explanation , but somehow i am unable to eliminate option A, don't know why but when i negate it , it seems that if there are some birds of prey who also live in spiny cactus then owl might change their mind and they will not make home for the winter , isn't it also a assumption ? i think i am overthinking ): please help to understand

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Re: The dwarf masked owl, a rare migratory bird of prey, normally makes it [#permalink]

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New post 19 Mar 2017, 05:33
nks2611 wrote:
hii , expert although i got the right answer for this and understood the above explanation , but somehow i am unable to eliminate option A, don't know why but when i negate it , it seems that if there are some birds of prey who also live in spiny cactus then owl might change their mind and they will not make home for the winter , isn't it also a assumption ? i think i am overthinking ): please help to understand

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Hi,
But why would you even consider option A? It's not relevant to the argument that the owl will not come to the Baja peninsula unless something is done to revive the cacti population.

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Re: The dwarf masked owl, a rare migratory bird of prey, normally makes it [#permalink]

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New post 19 Mar 2017, 07:52
vikasp99 wrote:
The dwarf masked owl, a rare migratory bird of prey, normally makes its winter home on the Baja peninsula, where it nests in the spiny cactus. In fact, there are no other suitable nesting sites for the dwarf masked owl on the Baja peninsula. But a blight last spring destroyed all of the spiny cacti on the Baja peninsula. So unless steps are taken to reestablish the spiny cactus population, the dwarf masked owl will not make its home on the Baja peninsula this winter.

The argument depends on assuming which one of the following?


The argument:
(1) The dwarf masked owl nests in the spiny cactus on the Baja peninsula.
(2) No spiny cactus on the Baja peninsula => the dwarf masked owl will not make its home.

(A) No birds of prey other than the dwarf masked owl nest in the spiny cactus.
This choice is irrelevent to the passage. Even if only dwarf masked owl nests in the spiny cactus, this choice can't explain the argument that "the dwarf masked owl will not make its home on the Baja peninsula this winter".

(B) If the Baja peninsula contains spiny cacti, then the dwarf masked owl makes its winter home there.
This one restates argument (2) in opposed way. However, this one can't help to explain the argument.

(C) On occasion the dwarf masked owl has been known to make its winter home far from its normal migratory route.
This choice is irrelevant to the argument. If this choice is true, then the dwarf masked owl doesn't make its home on the Baja peninsula because of other reasons than lack of the spiny cacti.

(D) The dwarf masked owl will not make its winter home on the Baja peninsula only if that region contains no spiny cacti.
This one restate argument (2) with absolute tone: no spiny cacti is the only reason that the dwarf masked owl doesn't make its winter home on the Baja peninsula. In the passage, we can't know that the spiny cacti is the only and important requirement of the dwaft masked owl or not. The passage just mentioned that normally they nest in the spiny cacti.

Absolute tone is often wrong in GMAT.


(E) Suitable nesting sites must be present where the dwarf masked owl makes its winter home.
Correct as this choice links the argument (2) with (1).
This kind of bird nests in the spiny cactus, this means that the spiny cactus are suitable nesting sites for the dwarf masked owl. No spiny cactus means no suitable nesting sites => the dwarf masked owl can't nest on that region => they will not make home on there.

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Re: The dwarf masked owl, a rare migratory bird of prey, normally makes it [#permalink]

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New post 05 May 2017, 21:05
I am in trouble in applying negation technique here. Would you please help me?

D. The dwarf masked owl will not make its winter home on the Baja peninsula only if that region contains no spiny cacti.
Negated Statement: The dwarf masked owl will not make its winter home on the Baja peninsula only if that region contains spiny cacti.
Breakdown the conclusion. So, it is a valid assumption.

E. Suitable nesting sites must be present where the dwarf masked owl makes its winter home.
Negated Statement: Suitable nesting sites must NOT be present where the dwarf masked owl makes its winter home.
Breakdown the conclusion. So, it is a valid assumption.

Could not choose one from D and E

Moreover, just to learn

If question asks which one is the weakener, would D be a weakener?
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The dwarf masked owl, a rare migratory bird of prey, normally makes it [#permalink]

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Mahmud6 wrote:
I am in trouble in applying negation technique here. Would you please help me?

D. The dwarf masked owl will not make its winter home on the Baja peninsula only if that region contains no spiny cacti.
Negated Statement: The dwarf masked owl will not make its winter home on the Baja peninsula only if that region contains spiny cacti.
Breakdown the conclusion. So, it is a valid assumption.

E. Suitable nesting sites must be present where the dwarf masked owl makes its winter home.
Negated Statement: Suitable nesting sites must NOT be present where the dwarf masked owl makes its winter home.
Breakdown the conclusion. So, it is a valid assumption.

Could not choose one from D and E

Moreover, just to learn

If question asks which one is the weakener, would D be a weakener?


I am no expert but I would like to reply (please correct me if I am wrong):
The reason that "D" is wrong is simple: it's the repetition of the premise given in the argument. An assumption must bridge a gap or some sort of new information must be there and should directly attack the conclusion. Option "D" doesn't bring any new information, it's just the stated premise. Thus option "E" should be correct.

Option "D" should strengthen the conclusion instead of weakening it because by stating that "ONLY" if cacti are present, the owl will make its home. Thus it is removing any alternate possibility that the owl will make its home on any other thing other than the cacti.
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Re: The dwarf masked owl, a rare migratory bird of prey, normally makes it [#permalink]

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New post 06 May 2017, 15:26
Quote:
I am in trouble in applying negation technique here. Would you please help me?

D. The dwarf masked owl will not make its winter home on the Baja peninsula only if that region contains no spiny cacti.
Negated Statement: The dwarf masked owl will not make its winter home on the Baja peninsula only if that region contains spiny cacti.
Breakdown the conclusion. So, it is a valid assumption.

The negated statement here is slightly incorrect. Choice D says that the ONLY reason the dwarf masked owl will not make its winter home on the Baja peninsula is if that region contains no spiny cacti. To truly negate this statement, you would have to say something like, "Not having spiny cacti in the region is NOT the ONLY reason why the dwarf masked owl will not make its winter home on the baja peninsula." For example, what if the region contains spiny cacti but becomes infested with animals that eat dwarf masked owls or their eggs? Having spiny cacti in the region is a NECESSARY requirement but it is not necessarily a SUFFICIENT requirement (for more information on sufficient vs necessary, see this thread: https://gmatclub.com/forum/a-sufficient ... 50740.html). Using the negation technique can be tricky in these cases, so make sure you understand what needs to be negated!
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Re: The dwarf masked owl, a rare migratory bird of prey, normally makes it [#permalink]

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New post 06 May 2017, 15:27
vikasp99 wrote:
The dwarf masked owl, a rare migratory bird of prey, normally makes its winter home on the Baja peninsula, where it nests in the spiny cactus. In fact, there are no other suitable nesting sites for the dwarf masked owl on the Baja peninsula. But a blight last spring destroyed all of the spiny cacti on the Baja peninsula. So unless steps are taken to reestablish the spiny cactus population, the dwarf masked owl will not make its home on the Baja peninsula this winter.

The argument depends on assuming which one of the following?

(A) No birds of prey other than the dwarf masked owl nest in the spiny cactus.

(B) If the Baja peninsula contains spiny cacti, then the dwarf masked owl makes its winter home there.

(C) On occasion the dwarf masked owl has been known to make its winter home far from its normal migratory route.

(D) The dwarf masked owl will not make its winter home on the Baja peninsula only if that region contains no spiny cacti.

(E) Suitable nesting sites must be present where the dwarf masked owl makes its winter home.


Great question! It really made me focus on the finer details of the answer choices. Following is my reasoning to get to the correct answer (E):

Observation: the argument talks about owls that seek a proper nesting ground to build a winter home. So, if owls are given or they find an appropriate nesting ecosystem, they will build a suitable home for themselves. Essentially, we don't care about what is actually a winter home for the owl once the owl is given a proper nesting ground, and this is the assumption.

A: Talks about comparing other birds - out of scope
B: gives the same premise as given by the argument
C: talks about an alternate nesting strategy - out of scope

Now the two options that have caused the most confusion:
D: this option is similar to B and is actually a premise not an assumption - remember, a fact/truth cannot be an assumption
E: this is actually the assumption, if the owls are given proper nesting ground (no matter where the nesting ground is situated), the owls will happily build a nice winter villa for themselves

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Re: The dwarf masked owl, a rare migratory bird of prey, normally makes it [#permalink]

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New post 02 Aug 2017, 22:53
Ooooooh I really enjoyed this one. A great quality question. My 2 cents on negation and assumption:
Premise - The dwarf masked owl, a rare migratory bird of prey, normally makes its winter home on the Baja peninsula, where it nests in the spiny cactus. In fact, there are no other suitable nesting sites for the dwarf masked owl on the Baja peninsula.
Premise 2 - But a blight last spring destroyed all of the spiny cacti on the Baja peninsula.
Intermediate conclu - So unless steps are taken to reestablish the spiny cactus population, the dwarf masked owl will not make its home on the Baja peninsula this winter.
Actual assumption - link b/w nesting and cacti. Cacti = nesting place

The argument depends on assuming which one of the following?

(A) No birds of prey other than the dwarf masked owl nest in the spiny cactus. Nope - not connection to why these birds wouldnt come

(B) If the Baja peninsula contains spiny cacti, then the dwarf masked owl makes its winter home there. Already stated, cannot be assumed

(C) On occasion the dwarf masked owl has been known to make its winter home far from its normal migratory route. Inference

(D) The dwarf masked owl will not make its winter home on the Baja peninsula only if that region contains no spiny cacti. Reverse of what is stated, so not an assumption

(E) Suitable nesting sites must be present where the dwarf masked owl makes its winter home.YES - this links nesting with cacti - calls it 'only suitable site' - so if we negate this - that is, other habitat is also there then the birds may come back to the peninsula

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Re: The dwarf masked owl, a rare migratory bird of prey, normally makes it [#permalink]

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New post 03 Aug 2017, 01:46
Imo E
The necessary assumption is that there must be some suitable nesting sites present in Baja peninsula for the owl to make its home in peninsula.


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Re: The dwarf masked owl, a rare migratory bird of prey, normally makes it   [#permalink] 03 Aug 2017, 01:46
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