Knewton Challenge Discussion – GMAT Critical Reasoning (Kangaroo Joeys)

Posted on November 8, 2010 by Knewton

116

Here’s a tough Critical Reasoning question from CR2, Extra Practice HW1 (Assumptions). So far, 67.6% of students have missed it. How would you solve it?

Give it a shot, then share your answers, questions, and thought processes in the comments below. Remember, if you’re in our GMAT class now, add your teacher name and session to your comment (e.g., Zwelling, MW 1:30).

Update: When you’re ready to see the answer, check out Rich’s video explanation below!

A newborn kangaroo, or joey, is born after a short gestation period of only 39 days. At this stage, the joey’s hind limbs are not well developed, but its forelimbs are well developed, so that it can can climb from the cloaca into its mother’s pouch for further development. The recent discovery that ancient marsupial lions were also born with only their forelimbs developed supports the hypothesis that newborn marsupial lions must also have needed to climb into their mothers’ pouches.

The argument in this passage relies on which of the following assumptions?

[A] All animals that are born after a short gestation period are born with some parts of their bodies underdeveloped.
[B] Well developed forelimbs would have been more advantageous to ancient marsupial lions than well developed hind limbs would have been.
[C] If the newborn marsupial lion did not climb into its mother’s pouch, then paleontologists would be able to find evidence of this fact.
[D] Newborn marsupial lions that crawled into their mothers’ pouches could not have done so had they not had only their forelimbs developed at birth.
[E] Newborn marsupial lions would not have had only their forelimbs developed if this development were of no use to the marsupial lions.

Good luck! And don’t forget to try the rest of our GMAT Challenge Discussions once you give this one a shot. Got your answer? Check out the video to see how you did:

Posted in Challenge Discussions, GMAT, Verbal Guide | 116 comments

Anonymous

After analyzing for 2 minutes, I think it is between D and E. Without wasting much time, I will pick E.
Sunita Satpathy

My answer is E.

My cue was the word “needed”. It sounds like because the lions needed to climb into the pouch, they developed only forelimbs.
Vijay Uict

Answer is E…..Assumption is that forlimbs are developed for some purpose….so this developement is somway used in marsupial lions
Bansalra

MY answer is E …Rakesh Bansal
Suvankar Mishra

The answer is
Roy

Ans: D
Hemantofkanpur

My answer is D
sf

I think it’s A. The question is asking what is the underlying assumption that supports the hypothesis. The hypothesis is proposing that because the forelimbs were developed but the hindlimbs were not, the lions must have had a short gestation period and required further development by climbing into their mother’s pouch.
Kush

I was stuck between D and E; i choose E
Ren

I pick E
Souma Nag

Conclusion: The recent discovery ……. supports the hypothesis that newborn marsupial lions must also have needed to climb into their mothers’ pouches.
Premise: A newborn kangaroo, or joey, is born after a short gestation period of only 39 days.
Premise: At this stage, the joey’s hind limbs are not well developed, but its forelimbs are well developed, so that it can can climb from the cloaca into its mother’s pouch for further development.
Assumption: marsupial lions had their fore limbs developed to climb into their mothers’ pouches.
Option E
Fdecazaux

My answer is E.
I have hesitated between D and E.
But D admits as a fact that marsupial lions climb into their mothers’ pouches as it is a question.
So I choosed E.
Nick

I would say E…What the paragraph is essentially trying to convey is that forelimbs are needed for further development of a new born.
- Rshekhar02
  
  what the para is trying to convey is in the last sentence. only because of “only forelimbs”, marsupial lions were able to climb. don’t try to read the hidden meaning in CR. just rephrase what they say. that’ll be your conclusion.
Michmobi

I agree that it is E. D is tempting but the to say that newborns could not climb into a pouch if they had not had ONLY their forelimbs developed is not logical. They could theoretically climb into a pouch if other parts were developed as well.
- Rshekhar02
  
  in critical reasoning, you should concentrate only on what is said in the paragraph, not on what you already know. so it doesn matter if They could theoretically climb into a pouch if other parts were developed as well. look for the conclusion, look for the premise (why is the conclusion true according to the author), look for the gap between the two.
Akshay Minhas

Mine is “”as it mentions in passage “but its forelimbs are well developed, so that it can can climb from the cloaca into its mother’s pouch for further development”. so forelimbs were an advantage for further devolopment.
Akshay Minhas

Mine is “”as it mentions in passage “but its forelimbs are well developed, so that it can can climb from the cloaca into its mother’s pouch for further development”. so forelimbs were an advantage for further devolopment.
Pierre Enokou

pierre
I think it’s A
Pierre

Changed my mind. I am picking E
pragga

I would say the answer is E.
razziev

Answer is “D”
The conclusion about marsupial lions can only be supported with the following assumption
Only Developed forelimbs –> Climb into pouch
No only developed forelimbs –> No climb into pouch
Only option D explicates this assumption. Option E is out of scope since other uses of developed forelimbs are not discussed.
Arjun

d or e….. will pick e as it is a hypothesis
Nehavbsingh

it’s undoubtedly B
- Atb135
  
  I agree with you Neha. I feel that most of the people are missing out on a key point that is mentioned in the argument “forelimbs are well developed for Joey” where as most of the answer choices just say about development.
  
  So the assumption must be that only WELL developed forelimbs help in climbing into the mother’s pouch.
Nawshed_901ali

Nawshed
I think it is A
Michael_rideout

D is the answer
bamba kassim

the answer is E
Ksmith-10

I think it is E
Ksmith-10

how do we find out the real answer?
- Anonymous
  
  Once everyone has a chance to try it out, one of our Knewton teachers will weigh in to steer things in the right direction. Stay tuned!
Beachman101

Answer is B
Martin Kaczynski

IMO, I say it’s D.

The answer choices CAN introduce new evidence and are assumed true. With this in mind, “Newborn marsupial lions that crawled into their mothers’ pouches…” is new evidence that supports the joey scenario, and “…could not have done so had they not had only their forelimbs developed at birth” supports the the scenario as well.
- Martin Kaczynski
  
  …negating this assumption also causes the resoning to fall apart in the question.
Rajiv Singal

‘E’
‘D’ is pretty close, but saying “Newborn marsupial lions that crawled into their mother’s pouches” is assuming hypothesis to be a fact. So it is ruled out. Rest drift away from the point.
- Rajiv Singal
  
  First statement is a cause & effect. The second statement abour marsupial lions, identifies the same cause & assumes it led to the same effect!
Meagsconsedine

E–mostly by ruling out the others as not applicable.
Lianna Wolfson

D -
Grace

D! definitely!!
Rshekhar02

The conclusion is that marsupial lions climbed into thier mother’s pouch. Premise is that they had only forelimbs developed and that even joeys have only forelimbs well developed. Two assumptions are made: marsupial lions climbed only because they had only forelimbs. 2nd – marsupial lions and joeys are similar. so look for something on the lines of these two.

a. “all” is wrong. we are talking of only the marsupial lions and joeys.
b. we are not talking about advantages. we are looking for cause or analogy.
c. don’t get fooled by the first half. we are looking for cause or analogy. paleontologists’ ability to find evidence is irrelevant.
d. reframe this sentence. it says marsupial lions climbed because they had only forelimbs. this is what we were looking for.
e. this gives us a reason for the forelimbs, but our conclusion talks about reason for climbing. this is tricky.

If you keep an eye out for “climb because of only forelimbs” and “marsupial lions=joeys”, it is very easy to eliminate choices and arrive at answer d even if you didn’t understand it correctly.
Christian

The answer is D
PhadkeSurya

answer is d …
Mangalritesh01

I think it is D
Preeti

I feel the answer is D
Debajyoti Biswas

E is the right answer according to me.
Iulianvasilca

the answer is statement: A)
Deajyoti Biswas

E is the right answer.
Umar

Is ‘D’
Guest123

Even without ruling out other answers first, E is the only one that makes sense. The argument could be thought of as: “considering that only event B happened after event A to produce event C, event B must have been important/necessary.” In the text, “considering that marsupial lions developed only their forelimbs (event B) after their birth (event A), this development must have been important/necessary (so they can climb back to their mothers’ pouches for further development (event C)).” Choice E says the same thing.

As for D, I’m pretty those lions that climbed back COULD (as opposed to “would”) have done so just as easily (or even more effortlessly) had they not had only (meaning more than) their forelimbs developed.

Just my thoughts. Of course, any of the choices COULD be right.
Vbrenner

Answer is D
Lisakay

you don’t really need a knewton teacher to steer the discussion. the answer is e
Chezaya

I go for T
Chezaya

sorry D, i mean not T
Paulamidas 16

I think the answer is D
Zingha Lucien

The answer is E
Vamsi Emeperor

My answer is E
DJ

I think C..”newborn marsupial lions must also have needed to climb into their mothers’ pouches.” These scientists have already assumed that these lions needed to climb into their mothers’ pouches, and to have already done this they must believe that they would have found evidence to the contrary of they didn’t need to.
RJS

The answer choice is E. The second sentence provides context as to the reasoning for only the joey’s forelimbs development at birth, the pouch is used for further development after birth. E correctly states that newborn marsupial lions would not have had only their forelimbs developed if “this development” (the use of the mother’s pouch for further development after birth) were of no use.

If you look at answer choice D, it would be the obvious correct answer if you took out the word “only” (Newborn marsupial lions that crawled into their mothers’ pouches could not have done so had they not had their forelimbs developed at birth.) Adding the word only rephrases the sentence to state that the development of other body parts at birth would not allow the newborn to crawl into their mother’s pouches. Since only the forelimbs are necessary for the newborns to climb into the pouch, the development of other body parts is irrelevant.
Srivicool

i go with D. can anyone tell the OA please ?
Mama

D or E

I will go for D
Jackie

My answer is E
Anonymous

Answer should be D…
As in assumption question.. the negation of the option which weekens the conclusion is the correct.

Negation of D says: Newborn marsupial lions could have crawled into mother’s pouch without their forelimbs developed at birth….

This weakens the conclusion on which the argument is based. Hence this is the assumption
Anonymous

Answer D..

Negation of D .. weekens the conclusion.. Hence it is the only assumption…. E gives extra information.. not needed.. B, C out of leage… A is too strong
EBE

I’d go for C
Tawfiq_alsharjabi

The answer is E
deep

I go with E because necessity has caused development
Aditya (adinsane)

Premise: Joey’s well developed forelimbs are used to climb into mother’s pouch
Conclusion: Lions had the need to jump into their mothers pouches as they have their forelimbs developed just like that of joey

Most of us have rightly zeroed in on D and E, so I will carry on from there.
Both D and E use double negatives. So effectively they are positive statements as:
[D] Newborn marsupial lions that crawled into their mothers’ pouches could HAVE done so had they HAD only their forelimbs developed at birth.
[E] Newborn marsupial lions would HAVE had only their forelimbs developed if this development were of USE to the marsupial lions.

D says, the lions crawl into pouch, only if they have forelimbs developed. But the argument is all about if they really did crawl/climb?
E says the development of forelimbs happens only if its of some use (in this case ‘climbing’). This assumption rules out the possibility that the development of forelimbs may have happened even without any practical use. Hence, MY ANSWER: E
Piyush Agarwal

I feel its D…
Ravin4k

My answer is E
Hemanth

E it is. A, B and C are irrelevant. D is out of scope because something other than a forelimb is not being discussed.
Eckhard Stiller

The only two statements that make sense are “D” and “E”. D does not rule out, that masupial lions could have climbed into their mother’s pouches even if they had their hind limbs well developed along with their well developed front limbs. “E” is the answer of my choice.
ReemT

I think its E. The assumption is that forelimb development MUST have happenned for a reason, and that is not a valid assumption.
- K Seghier
  
  i am sorry . are you Rima from New Brunswik .
rm

=E
siiiid

I’d like to think it’s C.. Any thoughts?
Ngraveney

I’ll take E for 800.
Derick

I believe it is E. Development is the mother of Necessity.
Alex

Answers D
Sujay_kar

Answer is D.
Sandeepbkamath

i go with e
Ndokpascaline

my answer is d
harshi

E. Only this makes the assumption that forelimbs are developed for a reason.
Anoo Anand

D –> Newborn marsupial lions that crawled into their mothers’ pouches could not have done so had they not had only their forelimbs developed at birth.
Srdjan

E) This argument was made to support the evolutionary theory that animals develop certain abilities that helps them survive.
Anonymous

Amazing work, everybody!

The majority of comments here have narrowed the answer down to between choice D and choice E. Those people are…. absolutely right! As to which one it is- well, I don’t want to ruin the surprise. But I definitely like Aditya’s approach to evaluate the NEGATION of the assumptions as a way to see if the argument truly relies on them. Be careful; negating such convoluted answer choices can be tricky… the GMAT counts on it.

For the final answer, come to Knewton Office Hours this week, which is on Saturday at 11 am or Wednesday at 8 pm (both times are Eastern US time- we’re in New York!). We look forward to seeing you there!

By the way, this challenge discussion has been attempted by GMAT takers and Knewton students AROUND THE WORLD- see the top ten cities that have attempted this question here: http://www.knewton.com/blog/knewton/inside-knewton/2010/11/11/top-10-cities-checking-out-our-challenge-questions.

p.s. Dubai came in at #11- just under the top 10 cutoff- but we still love you, Dubai!
Jen

The answer is D
Laura

The answer B
Austin

I am going with A. because an assumption is based on facts as presented. and the hypothesis that is supported for the lions to have crawled in their mothers pouch assumes that are also undeveloped. As in C this argument gives the answer that if the lions did not climb into its mother’s pouch then scientist would be able to find evidence of this fact as dead undeveloped lions.
Samiracom Greche

I choose E
Sutapa

The answer is D. It uses the contrapositive strategy. If X relates to Y, then Not X relates to Not Y.

Allison SS 3pm
Vyse0403

I think it’s e
Frenzy_prash

answer is A
K Seghier

D , my response is also d
K Seghier

all things concidered , I believe it is c
S_mortazm

answer is A
http://twitter.com/madhurchadha madhur chadha

hundred percent E
Adi

Its D. Period.
Obi Son

Option [A] is wrong. Nothing is absolute. Development differ among different animals.
B. Correct answer. Seem plausble. Both marsupial had developed forelimbs. See also comment on option E
C. Wrong.Neither implied nor derived from the statement.
D is wrong. An animal can still ‘crawl’ if all four limbs are well develpoed.
E. Also wrong, Well developed forelimbs may be useful but that also suggests that underdeveloped hindlimbs could be to prevent the young ones from jumping far away and be exposed to predators. The underdeveloped hindlimbs in the end may be more advantageous than the developed forelimbs.
Mestrada4800

I would have to say d Because lions are different then kangaroo
Tharamuruganantham

my option is c.
Ravinder_jackd

Ans is D
Daniel

The answer is B

If the lions needed to climb into their mothers pouch with fore limbs

then it is because joeys have undeveloped hind limbs as well and climb into their mothers pouch.
K Ravikumar

Answer is A
Anujmanbjr

its D
http://www.knewton.com Knewton Team

Hey everyone,

If you’re ready to see the official answer, we just added a video explanation from Rich, one of our GMAT teachers. It’s posted right below the question, so check it out!
Noahlevin11

I got it right!
vic c

E is correct, because the author is saying the newborn marsupial lions developed their forelegs because they needed to climb into their mother’s pouches, so the correct answer is the assumption that the forelegs were developed for this specific purpose.
Dhriti89

very well explained!
thanks
Marsupial Lion

i got it right, kewl explanation !!
raviteja

good step by step procedure to kick the critical reasoning questions under timed condition. thumbs up.
emmanuella

wow, it all made sense. tanx a lot
abhishek

wow!!! i’ve done it ri8!!, but learnt a lot in understanding what really makes sense in choosing the right and eliminating the wrong… thanks for the explanation
kumud

i got it correct, thnx
Vladislav

The last two answers make me wanna puke on the man explaining. Answers ABC are of course incorrect, but D and E are kind of Lawyers sentences both which can be true or false if interpreted just a little differently. If D is dismissed because it doesnt state exactly that those forelimbs were needed (usage of the word COULD) then E should be dismissed because it doesn’t state anything specific at all and mentions foreLEGS – which are not even mentioned in the paragraph (mentioned are foreLIMBS which are not identified as legs or arms). So playing the lawyers game I assume that E is INCORRECT answer and D is closer to the truth. I hate these kinds of questions.
- G
  
  Could not have said it any better. I had exactly the same thoughts as you. This just pissed me off
Bob

I got it right and I’m in high school

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Knewton Challenge Discussion – GMAT Critical Reasoning (Kangaroo Joeys)

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