A plausible explanation of the disappearance of the

Yes, the answer is B. If dinosaurs would be unable to survive the aftermath of a comet, you'd expect the same to be true of similar animals, so B casts doubt on the theory. As for the other answers you asked about:

A just says "some people don't agree with the comet theory". You can rule those types of answers out right away. Whether a few people disagree with the theory is irrelevant; we need facts to weaken an argument, not opinions.

C just says "studying dinosaur skeletons doesn't help us to evaluate the theory". So skeletons don't give us any information about the comet theory. So C neither strengthens nor weakens the argument. If C instead said that a study of skeletons gives reason to think dinosaurs died from an alternative cause, then C would be a good answer, but that's not what it says.

@IanStewart. Though your comment about choice A makes sense, this info was new to me. To make your statement about choice A explicit, can we safely state that "Any opinion/belief/claim by an authority, whatever the status and credentials of the authority are, can't be used to disprove or raise doubt on author's opinion/belief/claim in an argument." ?

No,it doesn't work that way.Its just that the below statement is not strong enough to weaken the author's claim.
"One of the various schools of paleontology adheres to an explanation for the disappearance of the dinosaurs that is significantly different from the comet theory."
Also,in this statement,its just mentioned generally that the explanation differs to author's statement.If something concrete would've been mentioned,say something such as "X theory has stated that disappearance of dinosaurs took place because of Y reason" then we could have selected A.

Hope it helps,
Thanks!

In this question, A is particularly unhelpful, because all it says is that some people disagree with the theory. That's generally true about most theories. I suppose in a similar question, if one answer said something like "most experts who have researched this issue disagree with the theory", that kind of answer would help to weaken the argument. But for GMAT purposes, I don't think that matters -- I don't think I've ever seen a real GMAT question where that type of 'appeal to universal authority' answer was even among the answer choices. In every real GMAT weakening question I've seen, the correct answer is based on flaws or gaps in the argument itself, and not on the opinions of experts. And whenever I've seen answers that read something like "some people think X", those answers are never correct, because the logical force of an argument is not substantially diminished by the opinions of a few people.

Could somebody give a detailed explanation for why D is wrong?

I am confused between B and D.

Hi joshnsit

Could you please tell OA ? I would go with C

Question edited and OA added. This is an LSAT question, by the way.

I am not sure about B.

Argument is talking only about Dinosaurs not other species.
Species similar to Dinosaur may or may not survive in conditions specified but it will not weaken the argument.Even if we negate this it will not strengthen the argument.

If we negate choice A,it will strengthen the argument and hence is a weaker in original state.

Can someone tell me why "D) Many other animal species from the era of the dinosaurs did not become extinct at the same time the dinosaurs did." is not the correct answer? One possible explanation could be : since era is a long time period, it could mean that they existed in the same "era" as dinosaurs but didnt necessarily exist when the extinction happened. Is my thinking correct?

A plausible explanation of the disappearance of the dinosaurs is what is known as the comet theory. A large enough comet colliding with Earth could have caused a cloud of dust that enshrouded the planet and cooled the climate long enough to result in the dinosaur's demise.

Premise: A large enough comet colliding with Earth could have caused a cloud of dust that enshrouded the planet and cooled the climate long enough to result in the dinosaur's demise.
Conclusion: A plausible explanation of the disappearance of the dinosaurs is what is known as the comet theory

OK, so pretty straightforward argument. Honestly, given the amount of ways the LSAT could have spun this, it is best not try and "pre-think" this one out and just hope to see an alternate explanation or a weakener.

Which of the following statements, if true, most seriously weakens the argument?

A) One of the various schools of paleontology adheres to an explanation for the disappearance of the dinosaurs that is significantly different from the comet theory. -- OK, cool. So these two theories aren't compatible. But, who cares? There could be 50,000 theories that agree with us. So this ridiculous. Out.

B) Various species of animals from the same as dinosaurs and similar to them in physiology and habitat did not become extinct when dinosaurs did. -- I am usually skeptical of comparison answers, but let's analyze this a little more. It is a similar species, with similar living conditions, and yet they didn't go extinct. Hmm. They are similar in almost every way but the name. This does weaken it, because these fake-twins stayed around and our Dinos didn't. Both would have needed to go extinct to not weaken this. Bingo!

C) It can not be determined from a study of dinosaur skeletons whether the animals died from the effects of a dust cloud. -- Tricky answer choice. They are trying to make you assume that because we do not know if something occurred, that it didn't occur. But this cannot be assumed! Maybe we just don't have the technology to analyze the bones, but they really did die from this. We just don't know. Out.

D) Many other animal species from the era of the dinosaurs did not become extinct at the same time the dinosaurs did. -- This is why I pause with comparison answers. Look at this and please realize why this is different then B. These animal species could be completely different than our dinos. They could be a super species that developed a resistance to clouds and somehow learned to absorb dust for energy. The species are not the same, so they could be completely, ridiculously different. When species go extinct today on Earth, does every species go extinct? No. This is why this is wrong. We adapt to situations, just as these other species could. Out.

E) The consequences for the vegetation and animals of comet colliding with Earth are not fully understood. -- Once more, who cares? Does this mean the vegetation died off? And if so, does that meant the dinos were dependent on plants? We cannot make these assumptions. Out.

I am not able to eliminate option E

If consequences are not well understood, we cannot conclude anything about the impact of the collision on animals (I understand, it's irrelevant for vegetation), thus weakening the conclusion, right?

(I understand why B is right - so no issues there.)

IanStewart - Could you please shed some light on this? Thank you

First, be careful about rephrasing -- answer E says the consequences are "not fully understood", which is very different from saying the consequences are "not well understood". But more importantly, answer E says roughly "we don't know everything yet", but that's something we knew was true before reading the answer choices; if we did understand everything perfectly, we wouldn't need to speculate about why dinosaurs became extinct, because we'd know why it happened. So answer E can't really have any effect on the argument. You're really looking for a specific reason to doubt the argument in a question like this (as B provides), not an answer that says "scientists don't have a complete picture of how things work."

Thank you so much, Ian. I think I got the point.

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