I think A, B, and D are irrelevant.

Since the passage claims that 6 months was enough to freeze the dinosaurs and kill plants I drop C as well. E seems the right answer, since dinosaurs with respiratory problems could've easily died of contamination. And maybe the CO2 levels in the atmosphere were affected as well, killing the plants on the earth. (This last one is an assumption though.)

So, IMO E.

E... it gives a reason why the dinosaurs could have been killed off without depending on temperature or starvation. But also explains this would have been caused by the asteroid.. supporting the original claim

E.

critics welcomed.

Its E.

A assumes that the herbivorous dinosaurs became extinct. Yet we are told in the Q that the debris settled before plants died an thus there is no basis for concluding that the herbivorous dinosaurs became extinct.

B is completely irrelevant as is C.

D as others have mentioned the key-word here is many. The death of many dinosaurs is NOT equal to the extinction of dinosaurs.

E:This sentence explains why dinosaurs died from the impact even though the plants did not die and it wasn't cold enough for them to freeze to death. Therefore it solves the paradox.

Some scientists believe that 65 million years ago an asteroid struck what is now the Yucatan Peninsula, thereby causing extinction of the dinosaurs. These scientists have established that such a strike could have hurled enough debris into the atmosphere to block sunlight and cool the atmosphere. Without adequate sunlight, food sources for herbivorous dinosaurs would have disappeared, and no dinosaurs could have survived a prolonged period of low temperatures. These same scientists, however, have also established that most debris launched by the asteroid would have settled to the ground within six months, too soon for the plants to disappear or the dinosaurs to freeze.
Which one of the following, if true, most helps to resolve the apparent discrepancy between the scientists’ beliefs and the scientists’ results, as described above?
(A) Loss of the herbivorous dinosaurs would have deprived the carnivorous dinosaurs of their food source.
(B) Dinosaurs inhabited most landmasses on the planet but were not especially abundant in the area of the asteroid strike.
(C) A cloud of debris capable of diminishing sunlight by 20 percent would have cooled the earth’s surface by 7 to 10 degrees Celsius.
(D) The asteroid was at least 9.6 km in diameter, large enough for many dinosaurs to be killed by the strike itself and by subsequent tidal waves.
(E) Dinosaurs were susceptible to fatal respiratory problems cause by contamination of the air by asteroid debris.

E....

the paradox between the belief and the result is what needs to be resolved....

the belief is that the asteroid debris blocked sunlight resulting in a loss of vegetation and thereby extinction of dinosaurs.... and the result is that asteroid debris never blocked sunlight because the debris settled within six months of the collision event....

A. blocked sunlight and subsequent vegetation loss led to B. extinction (not true as explained in the argument)

which would mean that

A. (something else) led to B. extinction...

only E seems to offer an alternative explanation....

A. ok... but does not explain extinction.. only says the food chain got disrupted...
B. straightforward reject..
C. too many numbers (7 to 10 degree celsius) that are useless in explaining extinction
D. of course the asteroid may be large enough to kill "many" dinosaurs but does that necessarily mean extinction?
E. relates how the asteroid debris would have caused extinction.... asteroid debris -> air contamination -> "fatal" respiratory problems -> WIPEOUT....

Why is choice A wrong? I understood this choice as the carnivorous dinosaurs fed on herbivorous dinosaurs who became rare.

Can you please clarify?

Thanks

Choice (A) might be an accurate statement, but it does not explain the apparent discrepancy. The belief is that the asteroid would have "hurled enough debris into the atmosphere to block sunlight and cool the atmosphere." This would have caused the food sources for herbivorous dinosaurs to disappear.

BUT we seem to have a problem with this explanation: most debris launched by the asteroid would have settled to the ground within six months, too soon for the plants to disappear or the dinosaurs to freeze. If that's the case, what caused the extinction?


As stated in choice (A), it is certainly true that loss of the herbivorous dinosaurs would have deprived the carnivorous dinosaurs of their food source, but this does not explain the apparent discrepancy. We need something that explains why the herbivorous dinosaurs would have become extinct in the first place.


Since the debris settled within six months, the asteroid most likely did not eliminate the food sources. So how did the asteroid cause the extinction? Well, if the debris led to fatal respiratory problems, then that could have killed off all or most of the dinosaurs. Choice (E) resolves the apparent discrepancy and is the correct choice.
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E gives a reason to believe that asteroid was indeed the cause of dinosaur's death but not for the impact that asteroid had as discussed in the argument.

Sent from my SM-N960F using GMAT Club Forum mobile app

This doesn't make much sense. I chose correctly, but E does not support scientists' belief. Sure, the asteroid caused it, but not in the way scientists thought it would.

Posted from my mobile device

The scientists' belief is that dinosaurs' extinction was caused by the asteroid.

Some scientists believe that 65 million years ago an asteroid struck what is now the Yucatan Peninsula, thereby causing extinction of the dinosaurs. These scientists have established that such a strike could have hurled enough debris into the atmosphere to block sunlight and cool the atmosphere. Without adequate sunlight, food sources for herbivorous dinosaurs would have disappeared, and no dinosaurs could have survived a prolonged period of low temperatures. These same scientists, however, have also established that most debris launched by the asteroid would have settled to the ground within six months, too soon for the plants to disappear or the dinosaurs to freeze.

Which one of the following, if true, most helps to resolve the apparent discrepancy between the scientists’ beliefs and the scientists’ results, as described above?

Argument - Asteroid struck Peninsula --> debris were hurled into the atmosphere --> earth cooled + no sunlight = plants killed and loss of food source for dinosaurs. Thus cold weather + loss of food source = extinction.
Counter argument - the debris could have settled within 6 months- too soon for cold weather / loss of vegetation


(A) Loss of the herbivorous dinosaurs would have deprived the carnivorous dinosaurs of their food source.
- The argument states that 6 months are too less for complete loss of vegetation = sufficient food to avoid extinction of herbivorous dinosaurs. Thus the statement considers a situation that has not occured
- Wrong

(B) Dinosaurs inhabited most landmasses on the planet but were not especially abundant in the area of the asteroid strike.
- Does not relate the apparent discrepancy
- Irrelevant

(C) A cloud of debris capable of diminishing sunlight by 20 percent would have cooled the earth’s surface by 7 to 10 degrees Celsius.
- The argument clearly states that the loss in sunlight and cold temperature was not sufficient to affect the dinosaurs. This is just background extra information, in no way impacting the discrepancy
- Wrong

(D) The asteroid was at least 9.6 km in diameter, large enough for many dinosaurs to be killed by the strike itself and by subsequent tidal waves.
- We do not know if dinosaurs existed at the location of asteroid impact.
- Wrong

(E) Dinosaurs were susceptible to fatal respiratory problems cause by contamination of the air by asteroid debris.
- Asteroid strikes earth --> sends out debris --> the debris are inhaled by dinosaurs + debris are sufficient to affect entire earth as it is clearly mentioned that sunlight was blocked and temperature was cooled --> hence all dinosaurs were affected by the respiratory problem, which is fatal --> explains why this event did lead to extinction without affecting the food source to that extent.
- Correct

Dear Friends,

Here is the detailed explanation for this question-



Mind-map: Asteroid struck -> debris hurled -> sunlight blocked -> destruction of food for herbivorous dinosaurs + cold weather led to extinction -> but, debris would have settled too soon for plants to vanish and dinosaurs to freeze.

Missing link: Between belief that debris blocked sunlight and led to extinction and the result that debris would have settled too soon for plants to vanish and dinosaurs to freeze.

Expectation from the correct answer choice: To resolve discrepancy by suggesting why dinosaurs got extinct though plants did not vanish and dinosaurs did not freeze.

Choice A: This answer choice, in suggesting that the carnivorous dinosaurs were deprived of their food, assumes the extinction of herbivorous dinosaurs; however, the question clearly mentions that the scientists also established that the debris settled before the plants were destroyed and so there is no basis for concluding that the herbivorous dinosaurs became extinct; as it does not explain the reason for extinction and the apparent discrepancy, this answer choice is not correct.
Choice B: This answer choice focuses on areas inhabited by the dinosaurs and not on the reason for extinction or the discrepancy; hence, it is an irrelevant choice. By suggesting that dinosaurs were not especially abundant in the area of asteroid, this answer choice, if anything, is only complicating the discrepancy rather than resolving it.
Choice C: This answer choice focuses on some background information, which does not address the reason for extinction or the discrepancy in the argument; besides, the question clearly mentions that the lack of sunlight or the cold temperature was not enough to lead to the death of the dinosaurs; hence, this answer choice is extremely weak and fails to resolve the discrepancy; it is, therefore, not the correct answer choice.
Choice D: This answer choice mentions that “many” dinosaurs were killed by the strike and the subsequent tidal waves but that is not likely to lead to their extinction; as the answer choice does not explain the reason for extinction and address the discrepancy, it is not a fine answer choice.
Choice E: By suggesting an additional effect caused by the strike, this answer choice explains why the dinosaurs would have become extinct even though the plants were not destroyed and the temperature did not lead to the dinosaurs freezing to death; the debris was hurled into the atmosphere, inhaled by the dinosaurs, and affected their respiratory tract; this proved to be fatal and led to their extinction; as this answer choice addresses the discrepancy in the argument by explaining the reason for extinction, it is a fine answer choice.

Hence, E is the best answer choice.

To understand the concept of "Characteristics of an Explanation Statement on GMAT Critical Reasoning", you may want to watch the following video (~2 minutes):



All the best!
Experts' Global Team
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Between (D) and (E), we should notice key words:

(D) The asteroid was at least 9.6 km in diameter, large enough for many dinosaurs to be killed by the strike itself and by subsequent tidal waves.
The argument is concerned with explaining how the asteroid caused the EXTINCTION of dinosaurs, but this choice only talks about how the asteroid strike and subsequent tidal waves killed MANY dinosaurs. What about the dinosaurs that were NOT killed by the asteroid strike? (D) does not explain the discrepancy and hence is incorrect.

(E) Dinosaurs were susceptible to fatal respiratory problems cause by contamination of the air by asteroid debris.
(E) helps resolve the discrepancy: asteroid debris contaminated the air, causing FATAL respiratory problems to which dinosaurs were susceptible. (E) is correct. .
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(E) Dinosaurs were susceptible to fatal respiratory problems cause by contamination of the air by asteroid debris.

-- susceptible doesn't mean they actually experienced fatal respiratory problems
How is E correct?

Hi Blair

I like to repeat this: Our job is not to select the perfect or ideal answer option. Our job is to select the best answer option from among the options given.

Option (E) states that dinosaurs were susceptible fatal respiratory problems caused by X. The passage also states that X, in fact, did happen. Therefore, it is not a stretch to imagine that the dinosaurs did indeed suffer from those fatal respiratory problems. Option (E), while not perfect, does provide a plausible explanation for the paradox.

On the other hand, we cannot think of any scenario wherein any of the other options could explain the paradox stated in the passage. Therefore, among the given options, option (E) is the best one and hence the correct answer.

Hope this helps.
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