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Hey experts. I am really torn between A and B. Upon negating option B we get "no creatures that fly by flapping their wings have network of blood vessels in the skin of their wings". I think this fails the argument. The only reason I think its wrong because it also counters premise in the argument that "bats have blood vessels to dissipate heat". Is there something I am missing?

Thank you.
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Hey experts. I am really torn between A and B. Upon negating option B we get "no creatures that fly by flapping their wings have network of blood vessels in the skin of their wings". I think this fails the argument. The only reason I think its wrong because it also counters premise in the argument that "bats have blood vessels to dissipate heat". Is there something I am missing?

Thank you.


I have discussed this question in this video: https://youtu.be/ZQnhC4d5ODU

Also note that option (B) does not counter any premise but it is not correct.

Argument:
Bats have blood vessels... because they are needed to disperse heat ... because bats fly by flapping wings
Dinos have blood vessels...

Now we are concluding that dinos must have flapped their wings too. So we are assuming that their blood vessels were needed to disperse heat and that heat was created by flapping wings.

In a way we are assuming that anyone who has blood vessels in wings must fly by flapping wings.
Option (B) says that we are assuming that anyone who flies by flapping wings has blood vessels. Note that this is not our assumption. It is the reverse.

Also, negation of 'all' is 'not all.' It is not 'none'
All will come.
Negation: Not all will come.
means there will be some who will not come.
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Networks of blood vessels in bats' wings serve only to disperse heat generated in flight. This heat is generated only because bats flap their wings. Thus paleontologists' recent discovery that the winged dinosaur Sandactylus had similar networks of blood vessels in the skin of its wings provides evidence for the hypothesis that Sandactylus flew by flapping its wings, not just by gliding.

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


(A) Sandactylus would not have had networks of blood vessels in the skin of its wings if these networks were of no use to Sandactylus.

(B) All creatures that fly by flapping their wings have networks of blood vessels in the skin of their wings.

(C) Winged dinosaurs that flapped their wings in flight would have been able to fly more effectively than winged dinosaurs that could only glide.

(D) If Sandactylus flew by flapping its wings, then paleontologists would certainly be able to find some evidence that it did so.

(E) Heat generated by Sandactylus in flapping its wings in flight could not have been dispersed by anything other than the blood vessels in its wings.

Gave this as a prompt to ChatGPT and even it marked E as the correct answer. I told it that the OG answer was A, so it gave me another explanation as to why A is correct and E is incorrect. On further pointing out that it was contradicting itself, it gave the following explanation. Might be useful for folks juggling between A and E.
Attachments

File comment: Chat GPT on A vs E
Screenshot 2024-09-23 at 9.15.49 AM.png
Screenshot 2024-09-23 at 9.15.49 AM.png [ 300.58 KiB | Viewed 536 times ]

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argument structure is clear-
NW's ONLY purpose - to disperse heat during flight
Heat generated ONLY due to flapping

so firstly - we cannot question whether some other process generated heat or some other purpose of NW. we are given it in premise about their ONLY purposes so we cannot go against premise.

moving on, discovery is that WD had NW in wing's skin - hence it serves as evidence for flying by flapping and not by gliding.

plain and simple - author assumes that if NW present then It has to be of some work i.e., we cannot have a case that NW is present but its irrelevant or doesn't matter because if its the case then the author cannot say confidently that okay we found NW hence surely its evidence for flying by flapping and not gliding.

A - exactly, author assumes this as discussed above.

B - okay so flapping -> NW but does it mean all that have NW fly by flapping?? we don't know about the reverse thing.

C - fly effectively? don't care.

D - irrelevant to our conclusion - if anything then go use that evidence LOL.

E - if there were other methods to disperse heat is irrelevant, we are not looking to question about if NW was the only method to disperse heat.

even if there was a method say X to disperse heat does it mean it was SUFFICIENT to disperse the heat alone? maybe it worked in conjunction with NW in that case the conclusion will still hold true. or even say it had 3 more standalone methods apart from NW to disperse heat? so what? it doesn't break the conclusion that NW's presence provides evidence of this hypothesis - NW may still be one of the methods.
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Hi abhimahna,
you are wrong in your analysis of E - although its wrong answer but your analysis is faulty -
according to premise - NW's only purpose is to disperse heat BUT according to you - "heat generated is dispersed ONLY by vessels". these two are different things. Author never implied what you are saying, he only mentioned what NW's sole purpose is, he never commented on "what all" methods can be used for heat dispersion so saying that " heat generated is dispersed ONLY by vessels" is wrong, it could be done by 100 different method which author never quoted.

E is wrong since sure - there could be 100 different methods to disperse heat but as long as NW is one of them our conclusion holds true.
abhimahna
gmatexam439
GMATNinja abhimahna GMATNinjaTwo

Please explain why "E" is wrong and why "A" is correct? Also, please give the correct negation of each option.

Regards

Hi gmatexam439 ,

Here I go :

The passage says

1) Vessels serve ONLY to disperse heat.
2) Heat is generated ONLY while flapping wings.

=> I flap my wings, heat is generated and now it MUST disperse out of my vessels.

Then it concludes, since dinosaurs had these vessels therefore they used to flew.

Come on! This is non sense. Having some body part doesn't mean we are going to use it, right? What if they had those features but they never used it?

Hence, my pre thinking assumption is If THEY have a body feature, they have to use it anyhow.

Statement A is doing the same. Let's negate it.

They have had networks even if they don't use it. Ohh WOW, my conclusion is broken. How dare author say they used to fly? Call him, I wanna talk to him. :)

Moving on to option E.

(E) Heat generated by Sandactylus in flapping its wings in flight could not have been dispersed by anything other than the blood vessels in its wings.

We are already told that heat generated is dispersed ONLY by vessels. So, saying the same thing in different manner won't do any benefit. E can never be the answer.

Let's negate it.

Heat generated could be dispersed by other things too. Come on!! I am trying to break my premise. I cannot do so. (Look at the implication I drew after writing my two premises above.)

Hence, E is 100% wrong.

Does that make sense?
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