• NEW! FREE Beat The GMAT Quizzes
    NEW! FREE Beat The GMAT Quizzes
    NEW! FREE Beat The GMAT Quizzes
    Hundreds of Questions Highly Detailed Reporting Expert Explanations TAKE A FREE GMAT QUIZ
  • 7 CATs FREE!
    If you earn 100 Forum Points

    Engage in the Beat The GMAT forums to earn
    100 points for $49 worth of Veritas practice GMATs FREE

    Veritas Prep
    VERITAS PRACTICE GMAT EXAMS
    Earn 10 Points Per Post
    Earn 10 Points Per Thanks
    Earn 10 Points Per Upvote
    REDEEM NOW

Pls come an instructor, thank you

This topic has 1 expert reply and 9 member replies

Pls come an instructor, thank you

Post
In the late 1980’s, the population of sea otters in the North Pacific Ocean began to decline. Of the two plausible explanations for the decline-increased predation by killer whales or disease-disease is the more likely. After all, a concurrent sharp decline in the populations of seals and sea lions was almost certainly caused by a pollution-related disease, which could have spread to sea otters, whereas the population of killer whales did not change noticeably.

Which of the following, if true, most seriously weakens the reasoning?

A. Killer whales in the North Pacific usually prey on seals and sea lions but will, when this food source is scarce, seek out other prey.
B. There is no indication that substantial numbers of sea otters migrated to other locations from the North Pacific in the 1980’s.
C. Along the Pacific coast of North America in the 1980’s, sea otters were absent from many locations where they had been relatively common in former times.
D. Following the decline in the population of the sea otters, there was an increase in the population of sea urchins, which are sea otters’ main food source.
E. The North Pacific populations of seals and sea lions cover a wider geographic area than does the population of sea otters.


Why A not E????

  • +1 Upvote Post
  • Quote
  • Flag
Legendary Member Default Avatar
Joined
15 Jan 2010
Posted:
2330 messages
Followed by:
26 members
Upvotes:
56
Facebook Logo
Post
tracyyahoo wrote:
In the late 1980’s, the population of sea otters in the North Pacific Ocean began to decline. Of the two plausible explanations for the decline-increased predation by killer whales or disease-disease is the more likely. After all, a concurrent sharp decline in the populations of seals and sea lions was almost certainly caused by a pollution-related disease, which could have spread to sea otters, whereas the population of killer whales did not change noticeably.

Which of the following, if true, most seriously weakens the reasoning?

A. Killer whales in the North Pacific usually prey on seals and sea lions but will, when this food source is scarce, seek out other prey.
B. There is no indication that substantial numbers of sea otters migrated to other locations from the North Pacific in the 1980’s.
C. Along the Pacific coast of North America in the 1980’s, sea otters were absent from many locations where they had been relatively common in former times.
D. Following the decline in the population of the sea otters, there was an increase in the population of sea urchins, which are sea otters’ main food source.
E. The North Pacific populations of seals and sea lions cover a wider geographic area than does the population of sea otters.


Why A not E????
Nice questions

_________________
I Seek Explanations Not Answers

  • +1 Upvote Post
  • Quote
  • Flag
Legendary Member Default Avatar
Joined
26 Jul 2011
Posted:
2789 messages
Followed by:
43 members
Upvotes:
206
Target GMAT Score:
700+
GMAT Score:
640
Post
Agree with Munda, Interesting question!
Am unable to figure out any weakening(most) option Sad

  • +1 Upvote Post
  • Quote
  • Flag
Legendary Member Default Avatar
Joined
15 Jan 2010
Posted:
2330 messages
Followed by:
26 members
Upvotes:
56
Facebook Logo
Post
Tracy i agree with the OA but have restrained from giving a reply because you have especially asked for an instructor

_________________
I Seek Explanations Not Answers

  • +1 Upvote Post
  • Quote
  • Flag
Legendary Member Default Avatar
Joined
26 Jul 2011
Posted:
2789 messages
Followed by:
43 members
Upvotes:
206
Target GMAT Score:
700+
GMAT Score:
640
Post
mundasingh123 wrote:
Tracy i agree with the OA but have restrained from giving a reply because you have especially asked for an instructor
Munda,

Its always good to pour in our thought, for it may be the point others are looking for.

  • +1 Upvote Post
  • Quote
  • Flag
Senior | Next Rank: 100 Posts
Joined
22 Sep 2010
Posted:
55 messages
Upvotes:
1
Test Date:
8 Oct
Target GMAT Score:
700+
Facebook Logo
Post
tracyyahoo wrote:
In the late 1980’s, the population of sea otters in the North Pacific Ocean began to decline. Of the two plausible explanations for the decline-increased predation by killer whales or disease-disease is the more likely. After all, a concurrent sharp decline in the populations of seals and sea lions was almost certainly caused by a pollution-related disease, which could have spread to sea otters, whereas the population of killer whales did not change noticeably.

Which of the following, if true, most seriously weakens the reasoning?

A. Killer whales in the North Pacific usually prey on seals and sea lions but will, when this food source is scarce, seek out other prey.
B. There is no indication that substantial numbers of sea otters migrated to other locations from the North Pacific in the 1980’s.
C. Along the Pacific coast of North America in the 1980’s, sea otters were absent from many locations where they had been relatively common in former times.
D. Following the decline in the population of the sea otters, there was an increase in the population of sea urchins, which are sea otters’ main food source.
E. The North Pacific populations of seals and sea lions cover a wider geographic area than does the population of sea otters.


Why A not E????
It has been explicitly stated in the passage that the population of seals and sea lions has declined sharply. the passage suggests that the reason for this decline is also disease. however, if we consider choice A which says "Killer whales in the North Pacific usually prey on seals and sea lions but will, when this food source is scarce, seek out other prey" we can infer that the killer whales must have first fed on seals and sea lions and when they (seals and sea otters) were less in number and hard to find killer whales shifted their focus on sea otters resulting in decline in sea otters' population. hence disease is not the reason for the decline. Weakens the reasoning.

Hope it helps!

_________________
Regards
Abhimanyu

  • +1 Upvote Post
  • Quote
  • Flag
Master | Next Rank: 500 Posts Default Avatar
Joined
28 Jul 2011
Posted:
416 messages
Followed by:
6 members
Upvotes:
28
Post
I think the question is interesting but easy also.
here below is my approach:-->

Before going to the choices, my contemplation about the stimulus:
1- For sure something that happened to other species can happen to otters as well but thats not always true.
2- Why can't whale eat otters. If I can put along a choice which supports this, objective achieved.

Thus I did zero in the choice A.

After that I rushed through other choices as I knew that A was the best one.

  • +1 Upvote Post
  • Quote
  • Flag
Master | Next Rank: 500 Posts
Joined
07 Jun 2011
Posted:
496 messages
Followed by:
1 members
Upvotes:
38
Facebook Logo
Post
tracyyahoo wrote:
In the late 1980’s, the population of sea otters in the North Pacific Ocean began to decline. Of the two plausible explanations for the decline-increased predation by killer whales or disease-disease is the more likely. After all, a concurrent sharp decline in the populations of seals and sea lions was almost certainly caused by a pollution-related disease, which could have spread to sea otters, whereas the population of killer whales did not change noticeably.

Which of the following, if true, most seriously weakens the reasoning?

A. Killer whales in the North Pacific usually prey on seals and sea lions but will, when this food source is scarce, seek out other prey.
B. There is no indication that substantial numbers of sea otters migrated to other locations from the North Pacific in the 1980’s.
C. Along the Pacific coast of North America in the 1980’s, sea otters were absent from many locations where they had been relatively common in former times.
D. Following the decline in the population of the sea otters, there was an increase in the population of sea urchins, which are sea otters’ main food source.
E. The North Pacific populations of seals and sea lions cover a wider geographic area than does the population of sea otters.


Why A not E????
The author of the argument suggests that between the two possible explanations for the diminishing number of the otters, the death of otters by pollution related diseases is the strongest. He goes on to support this claim by citing the sharp decline in sea lion population and suggests that the pollution could have spread to the otters too.

We are looking for,maybe, another reason for the decline in numbers of these species. This will weaken the authors claim that it was the pollution related diseases that caused the death of these creatures

Choice A provides just that evidence. This tells us that it was the killer whales that were responsible for the deaths of these sea creatures

Choice E doesn't help in weakening this claim

  • +1 Upvote Post
  • Quote
  • Flag

GMAT/MBA Expert

GMAT Instructor
Joined
22 Jul 2009
Posted:
641 messages
Followed by:
45 members
Upvotes:
162
GMAT Score:
760
Post
Weakening causal arguments (pollution caused sea otter deaths) is done via three shortcuts:

1. Reverse the causal relationship (sea otter deaths caused pollution, not likely)
2. Deny the cause (here is some proof it wasn't pollution that caused the deaths)
3. Find another cause (it's those darn killer whales again, eating our sea otters!)

Choice A is a #3.

  • +1 Upvote Post
  • Quote
  • Flag
Master | Next Rank: 500 Posts
Joined
05 Nov 2010
Posted:
279 messages
Followed by:
1 members
Upvotes:
15
Facebook Logo
Post
IMO: A

in this argument two events occur at the same time, the author consider them cause-effect relationship...the argument conclude that the disease which killed sea lions is a cause for decline in population of otters...
since the argument claims that certainly the cause of decline in sea lion population is disease ==> their population declined ==> according to the answer choice A the killer whales find their main food source rare ==> go for another prey ==> hunt more otters ==> alternative cause for decline in otter population than disease ==> weaken the argument

  • +1 Upvote Post
  • Quote
  • Flag
Master | Next Rank: 500 Posts
Joined
16 Jun 2010
Posted:
158 messages
Followed by:
1 members
Upvotes:
13
Post
tracyyahoo wrote:
Why A not E????
well the question asks us to weaken the conclusion.. the conclusion is that the otters have disappeared (died) due to diseases.
The question's premise states that there are ONLY two possibilities... one is death from disease and the other is due to predators..
so in order to weaken the conclusion we must try to proove that the deaths were caused by the predators.. only choice A does that

  • +1 Upvote Post
  • Quote
  • Flag
  • PrepScholar GMAT
    5 Day FREE Trial
    Study Smarter, Not Harder

    Available with Beat the GMAT members only code

    MORE DETAILS
    PrepScholar GMAT
  • Veritas Prep
    Free Veritas GMAT Class
    Experience Lesson 1 Live Free

    Available with Beat the GMAT members only code

    MORE DETAILS
    Veritas Prep
  • EMPOWERgmat Slider
    1 Hour Free
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    EMPOWERgmat Slider
  • Varsity Tutors
    Award-winning private GMAT tutoring
    Register now and save up to $200

    Available with Beat the GMAT members only code

    MORE DETAILS
    Varsity Tutors
  • Magoosh
    Magoosh
    Study with Magoosh GMAT prep

    Available with Beat the GMAT members only code

    MORE DETAILS
    Magoosh
  • Target Test Prep
    5-Day Free Trial
    5-day free, full-access trial TTP Quant

    Available with Beat the GMAT members only code

    MORE DETAILS
    Target Test Prep
  • Kaplan Test Prep
    Free Practice Test & Review
    How would you score if you took the GMAT

    Available with Beat the GMAT members only code

    MORE DETAILS
    Kaplan Test Prep
  • Economist Test Prep
    Free Trial & Practice Exam
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    Economist Test Prep
  • The Princeton Review
    FREE GMAT Exam
    Know how you'd score today for $0

    Available with Beat the GMAT members only code

    MORE DETAILS
    The Princeton Review
  • e-gmat Exclusive Offer
    Get 300+ Practice Questions
    25 Video lessons and 6 Webinars for FREE

    Available with Beat the GMAT members only code

    MORE DETAILS
    e-gmat Exclusive Offer

Top First Responders*

1 Brent@GMATPrepNow 40 first replies
2 Ian Stewart 40 first replies
3 Scott@TargetTestPrep 39 first replies
4 Jay@ManhattanReview 28 first replies
5 GMATGuruNY 25 first replies
* Only counts replies to topics started in last 30 days
See More Top Beat The GMAT Members

Most Active Experts

1 image description Scott@TargetTestPrep

Target Test Prep

159 posts
2 image description Max@Math Revolution

Math Revolution

90 posts
3 image description Brent@GMATPrepNow

GMAT Prep Now Teacher

58 posts
4 image description Ian Stewart

GMATiX Teacher

49 posts
5 image description GMATGuruNY

The Princeton Review Teacher

38 posts
See More Top Beat The GMAT Experts