#9 - Some scientists believe that 65 million years ago an

[mpoulson]

Hello,

Can you explain how to arrive at Answer E? I don't understand how it effectively resolves the paradox more so than D. Both seem to effectively lead to the death of a large group of dinosaurs. Or is this because E opens the door for extinction of dinosaurs? Thank you.

- Micah

[Clay Cooper]

Hi again Micah,

Another good question.

I think the explanation is pretty simple, and that you have identified it: answer choice E suggests the possibility of the extinction of all dinosaurs, while answer choice D does not.

I think that both answer choices deal with the causal paradox (between the belief that the asteroid somehow caused the extinction, but not via the plant-extinction route): D suggests another route by which the asteroid could have killed dinosaurs, and E suggests a third.

I think, essentially, that the explanation in E makes more sense than the one in D, for pretty much the reason you mentioned: a 9.6-km wide asteroid could undoubtedly kill a lot of dinosaurs, especially with its subsequent tidal waves - but that seems less likely to wreak global destruction than a dust cloud which (since we know it is widespread enough to block the sun and cool the earth) kills dinosaurs via respiratory means, all over the world.

I hope that helps, I think you understand this question pretty well.

[simonsap]

The key here is the scope of the stimulus and answer choices.

Stimulus talks about extinction of the dinosaurs as a result of the sasteroid strike in the Yucantan region. It does not specify that the extinction was localized (i.e. only killing dinosaurs in the area). Instead, it seems fair to assume we're talking about a global dinosaur extinction.

Looking at the answer choices
A is contradicted by the stimulus.
B is localized extinction
C. Contradicted by stimulus. This choice has 2 problems. Is the 20% restriction in sunlight and subsequent 10 degree cooling enough to cause extinction? Also the stimulus says that given the timelines provided, it would not have been sufficient to cause said extinction.
D "many" dinosaurs to be killed.
E - keeps our options open and explains why dinosaurs would have died after the dust settled. It doesn't narrow our scope to a local extinction. Therefore a safe answer choice.

[bonnie_a]

Hello, I chose D and I wasn't too sure why E was the correct answer. Is D wrong because it deals with "many" dinosaurs, not every or possibly the majority of them? On the other hand, E is correct because it gives a more concrete reason for their extinction which applies to all?

[atierney]

Hello Bonnie,

For this question the distinction between D and E is primarily one of scope; E contemplates a far-reaching effect, the debris dissolve into the atmosphere and cause difficulties over the six-month period for a large amount of dinosaurs, whereas the asteroid itself, even though large, would only kill the number of dinosaurs within the vicinity at the time of impact, indubitably less than the net effect of the debris spread out across the atmosphere for an extended period of time.

This question definitely presents unfriendly answer choices though, but more than that, it presents a rather disagreeable stimulus! It's not clear that a persuasive argument can be made, given the paradox, regardless of which answer choice you select, and thus, it's really a matter of trying to find the answer that addresses a way in which widespread extinction could occur from that which apparently caused minimal (relatively speaking) impact. In this case, as in ones similarly situated, choose the answer choice that contemplates the effect that would have the furthest-reaching results, furthest-reaching including time-dimensional considerations as well!