Paleontologists have discovered fossils of centipedes that are

I think the answer is E
Fossils of spiders we re found with respiratory systems suited only to breathe air but this does not tell anything about the centipedes and we can not assume that they also had similar system for breathing.

confused between D and E but I think I will go with D because option E states the possibility of centipede being land dweller by mentioning that the same rock had a spider fossil which was a land dweller along with centipede fossil and water dwelling animal fossil.

Paleontologists have discovered fossils of centipedes that are 414 million years old. These fossils are at least 20 million years older than the earliest land-dwelling animals previously identified. The paleontologists are confident that these centipedes lived on land, even though the fossilized centipedes were discovered in rock that also contained fossilized remains of animals known to be water-dwelling.

The paleontologists' view would be LEAST supported by the truth of which one of the following?

(A) The legs of the fossilized centipedes were particularly suited to being a means of locomotion on land. -- This says they were built to be on land, which supports our conclusion

(B) All of the centipedes that had previously been discovered were land dwellers. -- This, again, supports out conclusion based on history

(C) The rock in which the fossilized centipedes were found was formed from mud flats that were occasionally covered by river water. -- This says that fish fossils could have been placed with our creature well after our creature had already been fossilized. Therefore, this supports our conclusion

(D) Fossils of the earliest land-dwelling animals that had previously been identified were found in rock that did not contain fossilized remains of water-dwelling animals. -- So no other water-dwelling animals were found with other land-dwelling animals. This doesn't 100% weaken our conclusion, but it certainly doesn't support it. This is our answer

(E) Fossils of spiders with respiratory systems adapted only to breathing air were found in the same rock as the centipede fossils. -- This says that air-breathing species were found with our creature. This would support the idea, albeit not well, that our creature was land-dwelling, too. Thus, this supports or conclusion

I am confused between B and D.
B conclusion of "All of the centipedes that had previously been discovered were land dwellers." gives no proof that this will also be a land dweller.
Can someone explain

Please see my explanation above. If it is still insufficient, I will explain further.

Least support means polar opposite (weakens) in the case above. This type of question is good for LSAT but for GMAT one can not assume that one is supposed to elect the polar opposite. The right answer could be the one which supports but does the least among all options which support the argument.

The paleontologists' view would be LEAST supported by the truth of which one of the following?

Conclusion: Despite the fact that fossilized centipedes were discovered in rock that also contained remains of animals known to be water-dwelling, paleontologists are sure that centipedes lived on land.

We must find a choice that least support our argument, so the right answer choice could bea weak strengthener , an irrelevant option or a weakener.


(A) The legs of the fossilized centipedes were particularly suited to being a means of locomotion on land.

This one strengthen the theory that centipedes lived on land - Incorrect

(B) All of the centipedes that had previously been discovered were land dwellers.

This one is an irrelevant option. The fact that previously discovered centipedes were land dwellers does not prove anything about the new discovered fossils. - Incorrect

(C) The rock in which the fossilized centipedes were found was formed from mud flats that were occasionally covered by river water.

You can make several assumptions about this one, but the most relevant word in this sentence is "ocassionally", so you can say that this option actually strengthens the argument by saying that MOST of the time the land sorrounded by the mud flats was not covered by water. - Incorrect

(D) Fossils of the earliest land-dwelling animals that had previously been identified were found in rock that did not contain fossilized remains of water-dwelling animals.

Now we have something. Previous discoveries of the earliest land-dwelling animals did not contain fossilized remains of water-dwelling animals, so this options makes us doubt by stating that this discovery has a new trait (rock that also contained remains of animals known to be water-dwelling). If we have new information, why are we concluding that these fossilized centipedes were also land-dwellers? - Correct

(E) Fossils of spiders with respiratory systems adapted only to breathing air were found in the same rock as the centipede fossils.

Fossils of animals with respiratory systems found along the centipede fossils strengthen our conclusion. Incorrect

For those proponents of pre-thinking, this is the perfect Qn. No amount of pre-thinking can solve this. Instead, you waste time and worse, you are pre-inclined to a certain answer without even considering all the options.
I am really surprised at the number of proponents of that tactic.

And this is not a difficult qn at all. But, I guess people fell for it because it doesn't really fall into any of the "patterns" of Gmat. I got it right easily.

The underlined part of the sentence in the passage is what paleontologists believe. Anythings against that belief would not support their view. If one understands the passage the part in italics is probably a hint(only because of the way choices are present).
Have highlighted text in red and green to show which ones support or which one does not/least.

shrgmat
You are right about prethinking in this question but what matters is that whether we know various methods to solve questions.

Answer D.

A) strengthens
B) strengthens
C) weak weakener- use of the word occasionally and the fact we know nothing about formation of rocks in general and what this information really proves.

D) Correct- Remains of water dwelling animals are not usual thus supporting an argument that weakens the conclusion.

E) strengthens

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