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I know the OA is right, but I can't eliminate the option E.
Give me a solid reason why " E" is wrong?
OG11 Q89.... Do help
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Source: Beat The GMAT — Critical Reasoning |
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Premises: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 flaped 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.
The blood vessels in a bat's wings serve only one purpose: to disperse the heat generated by flapping.
The wings of Sandactylus had similar networks of blood vessels.
Conclusion:
Sandactylus must have flapped its wings.
The assumption is WHAT MUST BE TRUE for the conclusion to be valid.
Apply the NEGATION TEST.
When the correct answer choice is negated, the conclusion will be invalidated.
Answer choice A, negated:
Sandactylus would have had networks of blood vessels in the skin of its wings EVEN IF THESE NETWORKS WERE OF NO USE to Sandactylus.
If the networks of blood vessels were OF NO USE to Sandactylus, then the argument CANNOT conclude that these networks are evidence of wing-flapping.
Since the negation of A invalidates the conclusion, answer choice A is the necessary assumption: WHAT MUST BE TRUE for the conclusion to be valid.
The correct answer is A.
Answer choice E, negated:
Heat generated by Sandactylus in flapping its wings in flight could have been dispersed by something other than the blood vessels in its wings.
The negation of E suggests that Sandactylus could have dispersed the heat from wing-flapping in any number of ways, STRENGTHENING the conclusion that Sandactylus flapped its wings.
Since the negation of E does not invalidate the conclusion, eliminate E.
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Patrick_GMATFix
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The answer is A. I go through the question in detail in the full solution below (taken from the GMATFix App).
-Patrick
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swarnav999
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I am unable to copy you Patrick. :/
Stil cannot eliminate E option. Guess I didnt understand your explanation.
Stil cannot eliminate E option. Guess I didnt understand your explanation.
Patrick_GMATFix wrote:
The answer is A. I go through the question in detail in the full solution below (taken from the GMATFix App).
-Patrick
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Patrick_GMATFix
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I think the easiest way to eliminate E is to use the negation test. If you negate a real assumption, the conclusion will no longer make sense.
the argument uses the fact that a dinosaur had a network of blood vessels whose purpose was to disperse heat generated by wing flapping to conclude that since Sandactylus had similar blood vessels, it must have flown by flapping its wings.
The negated version of E: Heat generated by flapping wings could have been dispersed in other ways.
This has no impact on the argument. Maybe the heat could have been dispersed by a cooling water droplets as the bird flew through rainy clouds. So what? The author's argument remains unaffected; the dinosaur had these blood vessels because it flapped its wings, so since Sandactylus had similar blood vessels it must have flapped its wings also.
E cannot be an assumption because negating it does not cause the conclusion to fall apart.
the argument uses the fact that a dinosaur had a network of blood vessels whose purpose was to disperse heat generated by wing flapping to conclude that since Sandactylus had similar blood vessels, it must have flown by flapping its wings.
The negated version of E: Heat generated by flapping wings could have been dispersed in other ways.
This has no impact on the argument. Maybe the heat could have been dispersed by a cooling water droplets as the bird flew through rainy clouds. So what? The author's argument remains unaffected; the dinosaur had these blood vessels because it flapped its wings, so since Sandactylus had similar blood vessels it must have flapped its wings also.
E cannot be an assumption because negating it does not cause the conclusion to fall apart.
- Check out my site: GMATFix.com
- To prep my students I use this tool >> (screenshots, video)
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