A newborn kangaroo, or joey, is born after a short gestation period of

Conclusion -- > Only forelimbs developed means marsupial lions had a certain use for them.
Premise --> Developed forelimbs used by kangaroos for a certain use.
Assumption --> Reason for development same in both animals (or) Development useful in both animals.

clearly addresses this assumption adn also passes the LEN test.

Negating , we get:
Newborn marsupial lions may have had only their forelimbs developed even if this development were of no use to the marsupial lions.

This clearly kills the conclusion. If the development was useless, then we cannot say that the lions would have used them for a certain requirement.


Kudos Please... If my post helped.

After 1'40'', I can only eliminate A, B, C.
I didn't get the meaning of D and E, then I make a guess on D which is wrong.
I have a question here. After 1'30'', if you only eliminate 3 out 5 answers, you make a educated guess, or spend extra 1 more minute. I am really weak at RC. So I try to save as much time for RC by finish SC in 1 minute and CR in 1 minute and half. If I get stuck in CR for 1'30'', I usually POE as much as I can, then make a guess. Is that a proper way to do?

Sure. No point wasting too much time on one question. That said, during practice, ensure that you understand the logic used in every question and give as much time as required to do it.

I believe that both D and E fill the gap and hence can be considered right answers
Argument conclusion is: Only forelimbs develoved in new born Lion ----> These forelimbs must have been used for climbing in mother's pouch
Assumption: New born lions could only climb in mothers pouch by using these develoved forelimbs and there was no other way by which these Lions could climb in their mother's pouch

Negate D: Newborn marsupial lions (that crawled into their mothers’ pouches) could have done so had they not had only their forelimbs developed at birth (in simple words, New lions could climb in their mother's pouch even if they didn't have forelimbs)--This is exact match nad Hence weakens the argument

Negate E: As mentioned in earlier post will mean (in simple words): the forelimbs could not be there if there was not practical usage of forlimbs, this negation also weakens the argument.

Choice D is still somewhat nearer to the argument as it directly address the "climbing in mother's pouch" where as E discussed more in general. But Both D and E weaken the argument.

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 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.

Both 'D' AND 'E' appear to be contenders. Lets see them one by one.............

[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.
Means that if newborn marsupial have both forelimb and hind limb developed, they could not have been able to climb their mother's pouches. how can this be true? they may not have needed to climb now but to say thay they could not have climbed cannot be true...This assumption is not implied.....

[E] Newborn marsupial lions would not have had only their forelimbs developed if this development were of no use to the marsupial lions. This is the correct assumption. Forelimbs were developed so they could climb their mothers pouches for further development of their forelimbs....IT HAD A PURPOSE... Hence CORRECT...


Kudos if i could help please.....

No, (D) is not correct. Only (E) is the correct answer. Check out this post for a detailed explanation on this question:
https://www.gmatclub.com/forum/veritas-prep-resource-links-no-longer-available-399979.html#/2012/12 ... tatements/

Here is a post on Conditional Statements which you need to understand for this question (and many more such questions):
https://www.gmatclub.com/forum/veritas-prep-resource-links-no-longer-available-399979.html#/2012/11 ... tatements/

The magic word is "usage" here. Once I read the text, the assumption followed naturally: we need a link between the lion and the pouch. Skimming the question, I finally found the word "use" in E that matches my hypothesis.

E) Newborn marsupial lions would not have had only their forelimbs developed if this development were of no use to the marsupial lions

E answered perfectly to the argument by stating a new link between the lion and the pouch.

Hope it helps

Happy new year!

Really confusing answer choices.
Can experts also comment what is wrong with A?

Please find inline comments :
Premise: A newborn kangaroo forelimbs are well developed, so that it can can climb from the cloaca into its mother's pouch for further development.

Conclusion: 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.

Prethinking :

1. Forelimbs are not developed without any purpose to be served.

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.

It doesn't speak about developed bodies and the reason of their existence , hence OOS

(B) Well developed forelimbs would have been more advantageous to ancient marsupial lions than well developed hind limbs would have been.

it doesn't specify the use of forelimb in climbing , comaprision here doesn't affect conclusion , incorrect

(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.

Doesn't affect the conclusion that forelimbs are used to climb . , incorrect

(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.

It is not a assumotion and it is other way to say the conclusion () Incorrect

(E) Newborn marsupial lions would not have had only their forelegs developed if this development were of no use to the marsupial lions.

Correct answer , assert on the reasoning that the forelegs are developed for a purpose

An assumption is a statement that MUST BE true in order to link the premise with the conclusion. In this question:

Premise 1 (P1): Joey has developed forelimbs to climb into mother's pouch.
Premise 2 (P2): Marsuptial lions have developed forelimbs.
Conclusion (C): Marsuptial lions also needed to climb into mother's pouch.

Option A is not a mandatory link between P1/P2 and C, and hence not an assumption.

Hi VeritasKarishma,

Can you please verify whether my understanding is correct:
1) Premise for Joe, the kangaroo: Climb Mothers Pouch -> Fore Limbs
2) Conclusion for Marsupial Lions: Fore Limbs -> Climb Mothers Pouch.
3) Assumption: Fore Limbs are necessary to Climb Mothers Pouch.
4) Premise is for Kangaroos and Not close to what we need. Therefore new unstated evidence needed as assumption.
5) Assumption is the contrapositive in E.
6) Choice D just restates 1) for lions

Also,

if the premise for kangaroos were Fore Limbs -> Climb Mothers Pouch, would the assumption be on the lines of Kangaroos and Lions are similar, considering comparative reasoning ?

VeritasKarishma

Hi need your to help on the article written by you on necessary vs sufficient conditons.I have highlighted my doubts in bold.i am replicating your article here.

Question: 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 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.

Solution: Take some time to understand the argument first.

“A joey has a short gestation period but its forelimbs are well developed so that it can climb into its mother’s pouch for further development.”

The argument is telling you that the joey has a short gestation period (implying that it is not properly developed when it is born). It further states that the reason the forelimbs of a joey are well developed is that it needs to climb into its mother’s pouch. Notice the use of ‘so that’; it implies reason.

“marsupial lions were also born with only their forelimbs developed so newborn marsupial lions must also have needed to climb into their mothers’ pouches.”

It further states that marsupial lions were also born with only forelimbs developed. So they must have needed to climb into their mothers’ pouches too. The argument assumes here that forelimbs were developed for a reason (the reason is that they needed to ‘climb into their mothers’ pouches’). It assumes that if the lions did not have a need for the forelimbs to be developed, the forelimbs would not have been developed. Since the forelimbs were already developed at birth, it must have been for a reason. That is, developed forelimbs necessarily imply need to climb into mother’s pouch.

If you want to use the structure we learned in the last post, we can say that the assumption is similar to:

“Only if the marsupial lion needs to climb into its mother’s pouch will it have well developed forelimbs.”

How did u arrive at above assumption.
Cannot we read it like
If lions were born with only their forelimbs developed,marsupial lions must also have needed to climb into their mothers’ pouches.


or like
If marsupial lions must also have needed to climb into their mothers’ pouches,then were born with only their forelimbs developed.
I am confused here.

A – the marsupial lion needs to climb into its mother’s pouch

B – it has well developed forelimbs

In case of ‘only if,’ ‘not A implies not B’.

‘Not A implies not B’ is ‘the marsupial lion does not need to climb into its mother’s pouch implies it doesn’t have well developed forelimbs’

This is the assumption made. Let’s see which option says the same thing.

Option (E) states that “Newborn marsupial lions would not have had only their forelimbs developed if this development were of no use to the marsupial lions.”

This is equivalent to “if this development were of no use to the marsupial lions, newborn marsupial lions would not have had their forelimbs developed.”

In case of ‘if’, A implies B which means ‘there is no use of well developed forelimbs (no need to climb into mother’s pouch)’ implies ‘the forelimbs are not well developed’

This is the assumption we discussed above. Hence E is correct.

The only source of confusion is option (D).

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.

This is not correct. Our original argument says that developed forelimbs implies crawling into mother’s pouch. It doesn’t say that crawling into mothers’ pouches implies developed forelimbs. Notice that it has been found that these lions had developed forelimbs. The argument says that this implies that they crawled into pouches.

true that argument doesn’t say that crawling into mothers’ pouches implies developed forelimbs.
but it is given that they were developed only fr reason that they could crawl. So isnot development a prerequisite of crawling.

If we were given that it has been found that the lions crawled into their mothers’ pouches and that this implies that their forelimbs must have been developed, then we could have said that the argument is assuming what option D says. Since this is not the case, option D is not correct.

This is what the argument has given:

"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."

... lions must have needed to climb ...

So 'a need to climb' is NECESSARY for 'developed forelimbs'.
'Only if' conditions are 'necessary' conditions.

Only if a need to climb, then developed forelimbs.
Only if A, then B.
B -> A
A' -> B'

So 'developed forelimbs' implies 'a need to climb'.
'no need to climb' implies 'not developed forelimbs' (this is option (E))

B' does NOT imply A'
'No developed forelimbs' does NOT imply 'no crawling' (hence (D) is not correct)

VeritasKarishma
thank you so much ,it really helps

ok i have some generic queries on this

In it is given If A,then B where A is sufficient condition then in WEAEKNING qsns,if i show
there is some other C that causes B ,then it wont be weakener,Right? bcz a is sufficient condition
but if A is neceaasry condtion ,then if i show C leads to b then it will be weakener.

Also in INFERENCE questions /or STRENGTHEN questions ,
“If X, then Y”

if x is sufficeint thenn
if not x then not y will not be correct
but if x is necessry
then
if not x then not y will be correct.
Is my analysis right?

Correct.



If you are given that A is necessary for B and if you show that C leads to B (while A does not happen), then this makes the premise false. But you have to take the premise to be true.
If 'A is necessary for B' is the conclusion, and if you show that C leads to B (while A does not happen), then this makes the conclusion false.



In the 'only if' construct (Only if X, then Y), X is a necessary condition.
In the 'if' construct (If X, then Y), X is a sufficient condition.

Only if X, then Y
- Y implies X
- Not X implies Not Y

If X, then Y
- X implies Y
- Not Y implies Not X

Brilliant explanations. Thank you mam!
Also for the benefit of the community a question on the exact same logic from the official guide.
https://gmatclub.com/forum/networks-of- ... 35718.html

OPTION D logical analyses:

The argument's conclusion says ->
Marsupial Lions had developed forelimbs implies that they crawel into pouches.

Option D says:
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.

Which translates to ->
NO forelimbs developed at birth implies NO crawling into pouches. (Not B implies Not A)

However, this will only be true when->
Crawling into pouches implies forelimbs developed at birth. (A implies B)

This logic, however, is the reverse of what the passage says, as noted above, and hence, option D doesn't support the logic of the argument and is not a required assumption.

KarishmaB, would appreciate your feedback on my thinking