Its D as the structure present in lab is different from the previous one and hence the conclusion is weakened
_________________

Practice Practice and practice...!!

If my reply /analysis is helpful-->please press KUDOS
If there's a loophole in my analysis--> suggest measures to make it airtight.

Basically the thing is :
F found in lab first then in nature, as they can be synthesized in lab argument concludes that okay it is possible to know something about the earth's state when these naturally occurring F were found. But what about if geologists dont know there structure prior to the point when discovery was made then its useless having F in lab. Because its no concrete source to make the conclusion.

Previously Unknown means before the discovery nothing about the structure is known. Hence if nothing is known till that point we cant say anything regarding the conclusion and hence conclusion stands is weakened.

Hope this helps..!!
_________________

Practice Practice and practice...!!

If my reply /analysis is helpful-->please press KUDOS
If there's a loophole in my analysis--> suggest measures to make it airtight.

I also agree with the choice D, and the explanation of the guys above is enough for this question. Nice question. Thank all guys
_________________

Rules for posting in verbal gmat forum, read it before posting anything in verbal forum
Giving me + 1 kudos if my post is valuable with you

I can't understand either of options (except C, but that with a long shot) weakening the conclusion.

Argument says : Because F could be formed in Lab in distinctive conditions (of temperature and pressure), We should be able to evaluate earth crust's conditions as well at the time of these Fs formed naturally. So, It's essentially assuming F can be formed in a specific set of conditions.

Let's evaluate Options :
A. Confirming that the shungite genuinely contained fullerenes took careful experimentation
=> Not Related - No Impact

B. Some fullerenes have also been found on the remains of a small meteorite that collided with a spacecraft.
=> Even if some were found in a small meteorite, it doesn't impact the argument. Because that small meteorite may also have similar conditions as Lab had when F were formed.

C. The mineral shungite itself contains large amounts of carbon, from which the fullerenes apparently formed.
=> This makes a little sense for me because it gives an alternative reason to believe why F formed naturally had something special (large amount of carbon) which may not be there in the lab. So we might be able to say those conditions in which F formed may not be same/ similar in Lab and earth-crust.

D. The naturally occurring fullerenes are arranged in a previously unknown crystalline structure
=> Even if naturally occurring F are in crystalline structure unknown earlier, it is know now. And it doesn't give me any reason to say naturally occurring F would have different structure than the structure of Lab-formed F.
I can't understand how it would weaken the argument

E. Shungite itself is formed only under distinctive conditions.
=> Already stated a s part of premise, so essentially it's strengthening the argument, not weakening.

I'd appreciate expert views on this.
_________________

-------------------------------------------------------------------------------------------------------------------------------
http://gmatclub.com/forum/a-guide-to-the-official-guide-13-for-gmat-review-134210.html
-------------------------------------------------------------------------------------------------------------------------------

if this is the case, it helps the argument

Hi,

Can you please let me know how you have eliminated C.

My reasoning was as the fullerness is formed directly from rock, unlike in lab so conditions might be different during formation.......
_________________

+1 Kudos If found helpful..

Although fullerenes - spherical molecules made entirely of carbon - were first found in the laboratory, they have since been found in nature, formed in fissures of the rare mineral shungite. Since laboratory synthesis of fullerenes requires distinctive conditions of temperature and pressure, this discovery should give geologists a test case for evaluating hypothesis about the state of the Earth's crust at the time these naturally occurring fullerenes were formed.

Which of the following, if true, most seriously undermines the argument?
A. Confirming that the shungite genuinely contained fullerenes took careful experimentation
B. Some fullerenes have also been found on the remains of a small meteorite that collided with a spacecraft.
C. The mineral shungite itself contains large amounts of carbon, from which the fullerenes apparently formed.
D. The naturally occurring fullerenes are arranged in a previously unknown crystalline structure
E. Shungite itself is formed only under distinctive conditions