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­There are two ways to focus on the passage:   1. Static Jump   vs   2. Flight

Static jump:_________


P: Quetzalcoatlus needs 48+ kmph to take off, not possible from a standing jump

To prove Paleontologist(P) wrong Biomed researcher (BR) must provide an edivience that suggests :  Quetzalcoatlus needs 48+ kmph to take off, possible from a standing jump.

But if BR says: Quetzalcoatlus needs 48+ kmph to take off, possible by a combination of running + leaping ( option D )
this suggests: Quetzalcoatlus needs 48+ kmph to take off, possible by a combination of running + leaping ( P is right it's not possible from standing jump )

But this doesnot counter P's statement that Quetzalcoatlus can't take off just by jumping

To simply disprove / provide rebuttal to A we must say:  Quetzalcoatlus needs 48+ kmph to take off, possible from a standing jump ( by jumping off from a cliff  - option A )

Option A is correct as far as this line of reasoning is concerned 


Flight:____________ 

The BR actually concludes that "Quetzalcoatlus could fly", (wheather a static jump was involved or not is not the important aspect, it's an evidence in support). And the focus of P's argument is they can't fly ( by disproving that static jump can't give 48+ kmp speed ). But P overlooks the fact that flight is possible by a combination of (run + jump).

If the focus is on flight then Quetzalcoatlus can fly anytime they wish to, if they can take off by running and jumping, this provides additional evidence in support of flight ( option D )
But
If they need a cliff to jump off and fly, flight is dependent on Cliff, so that's could be called gliding ( option A )


If we reread the passage we will observe the subtle difference in the focus (on flight) , hence option D is the correct choice.­
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Answer choice A is what a lot of people chose but it can't be A due to the fact that the passage says the dinosaur leaps from all four "legs". If it dives off of something on its hind legs then it's not leaping with all four legs.

However, D still allows this fact to be true. In your head picture some winged dinosaur running on all fours and then jumping from all fours into the air.

Weird question but the answer is definitely D.­
­Weird question indeed! But wouldn't D imply that the pterosaur ran using all four legs to be in a position to be on its fours just before leaping or could we assume that it's running using two but just before it's about to leap, it falls on its four and leaps with all four?

Sounds weird and seems weird all along! :D
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Answer choice A is what a lot of people chose but it can't be A due to the fact that the passage says the dinosaur leaps from all four "legs". If it dives off of something on its hind legs then it's not leaping with all four legs.

However, D still allows this fact to be true. In your head picture some winged dinosaur running on all fours and then jumping from all fours into the air.

Weird question but the answer is definitely D.­
­Weird question indeed! But wouldn't D imply that the pterosaur ran using all four legs to be in a position to be on its fours just before leaping or could we assume that it's running using two but just before it's about to leap, it falls on its four and leaps with all four?

Sounds weird and seems weird all along! :D
­Yea possibly... I think the key takeaway here is that when you're stuck between A and D, answer choice A says the creature dives off its hind legs which are not all four of its legs therefore you'd eliminate A and that just leaves D as your answer.­

I wonder whether hindlegs is something a nonnative English speaker would usually understand or not. It's a weird term.
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I didn't choose D. as the passage said "However, this hypothesis is implausible, since Quetzalcoatlus had to attain a speed of at least forty-eight kilometers per hour to take off," and choice D. is just the direct opposite of what the passage say which is very strange to choose.
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­Paleontologist: The giant pterosaur Quetzalcoatlus had an eleven-meter wingspan and was too heavy to take off merely by flapping its wings, even with a running start. One biomechanics researcher found that Quetzalcoatlus had wings that were far sturdier than it would have needed during flight, and concluded that it took off by using the wings as forelimbs, beginning its flight by leaping with all four "legs." However, this hypothesis is implausible, since Quetzalcoatlus had to attain a speed of at least forty-eight kilometers per hour to take off, which would have been impossible from a standing jump.

Of the following, which, if true, would be the most effective rebuttal the biomechanics researcher could make to the paleontologist's argument?

A) Quetzalcoatlus could plausibly have taken off by diving off a cliff from its hind limbs, then using the fall to accelerate. - provides a new hypothesis rather than a rebuttal.

B) Most other pterosaur species are known to have taken off by flapping their wings after a running start. - "other pterosaur species" are out of scope.

C) The sturdy forelimbs of Quetzalcoatlus could have helped it to subdue its prey when not in flight. - out of scope.

D) Quetzalcoatlus could plausibly have run fast enough to take off by leaping into the air after a running start. - Yes. This means that the "giant pterosaur" still uses the same mechanism that the "biomechanics researcher" recommended - it took off by using the wings as forelimbs, beginning its flight by leaping with all four "legs." The "Paleontologist" assumes there is no other way by mentioning that it is "impossible from a standing jump." But this option highlights that a "giant pterosaur" could gain speed and then use limbs to leap into the air.

E) Researchers know of no plausible way in which any giant pterosaur species could have attained a speed of 48 kilometers per hour before taking off.­ - Weakner at best for biomechanics researcher.
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I didn't choose D. as the passage said "However, this hypothesis is implausible, since Quetzalcoatlus had to attain a speed of at least forty-eight kilometers per hour to take off," and choice D. is just the direct opposite of what the passage say which is very strange to choose.
­Well, we do want to oppose the argument. You're right that we don't usually do that by directly contradicting one of the author's premises. However, D doesn't do that. The original argument says that the leaping hypothesis is implausible because the dino couldn't achieve the needed speed for flight from a standing jump. D just points out that it *could* achieve that speed with a *running* jump. That's a different possibility that the author didn't address, so it effectively weakens the argument.
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I feel that everyone's response completely disregards the statement in the premise that clearly says the pterosaur "was too heavy to take off merely by flapping its wings, even with a running start". I was between A & D during my mock and went with A b/c D suggests the pterosaur would be able to fly from a running start which seemingly attacks a premise in the first sentence that I thought we are supposed to be taking as true. Can anyone help me understand where my logic is flawed?
ashutosh_73
­Paleontologist: The giant pterosaur Quetzalcoatlus had an eleven-meter wingspan and was too heavy to take off merely by flapping its wings, even with a running start. One biomechanics researcher found that Quetzalcoatlus had wings that were far sturdier than it would have needed during flight, and concluded that it took off by using the wings as forelimbs, beginning its flight by leaping with all four "legs." However, this hypothesis is implausible, since Quetzalcoatlus had to attain a speed of at least forty-eight kilometers per hour to take off, which would have been impossible from a standing jump.

Of the following, which, if true, would be the most effective rebuttal the biomechanics researcher could make to the paleontologist's argument?

A) Quetzalcoatlus could plausibly have taken off by diving off a cliff from its hind limbs, then using the fall to accelerate.
B) Most other pterosaur species are known to have taken off by flapping their wings after a running start.
C) The sturdy forelimbs of Quetzalcoatlus could have helped it to subdue its prey when not in flight.
D) Quetzalcoatlus could plausibly have run fast enough to take off by leaping into the air after a running start.
E) Researchers know of no plausible way in which any giant pterosaur species could have attained a speed of 48 kilometers per hour before taking off.­
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