Although fullerenes - spherical molecules made entirely of carbob-were first found in the lab, they have since been found in nature, formed in fissures of the rare mineral shungite. Since lab synthesis of fullereness requires distinctive conditions of temp and pressure, this discovery should give geologists a test case for evaluating hypothesis about the state of the Earth's crust at the time of these naturally occurring fullereness 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 the remains of a small meteorite that collided with a spacecraft.
C. the mineral shungite iteself contains large amount carbon, from which the fullerenes apparently formed
d. the naturally occurring fullerenes are arranged in a previously unknown crystalline strucutre
e. shungite itself is formed only under distinctive conditions.

Why D? What does "previously unknown" mean here anyway? Any new discovery is always "previously unknown". How does weaken the argument?

I think I saw this problem in OG as well, but I cannot find it now or GMAT prep threw the same question twice in two tests and I managed to get it wrong both the tiems :(

Take another look at that answer choice: It's the crystalline structure of the found fullerenes that's 'previously unknown'. That means that the fullerenes that have been discovered are fundamentally different from ALL other fullerenes that have ever been described - including all the ones that have ever been made in labs.
* This means that these particular fullerenes - the ones that have been found in the fissures - are chemically different from all the KNOWN classes of fullerenes.
* [KEY INFERENCE] That means that we don't know the 'distinctive conditions of temp and pressure' required to form the NEW kinds of fullerenes.
* Therefore, because of this ignorance, they don't constitute a test case for anything geological.

Hope that helps.

The (D) choice only makes sense with the assumption that the original fullerenes. discovered in the laboratory were not arranged in the same crystalline structure. And since there is no time line for fullerenes discoveries, other than first and since, one could think of those laboratory discovered fullerenes arrangements as of previously unknown ones. Could it be so that the molecules be found first and than their arrangement be discovered?

that's what the authors appear to imply via their use of the phrase 'previously unknown'.

remember, they make the test, so they make the rules (including determining the meanings of words and phrases as they see fit). so this is what 'previously unknown' means when they say it.




occam's razor applies here.

could it be? yes.

but which is the simpler, and more reasonable, assumption:
(1) the arrangement was discovered at the time of the molecule's discovery;
(2) the molecule was discovered, but the discovery of its arrangement was somehow postponed until later?

not only is (1) simpler, more sensible, and eminently more reasonable, but i don't even see how (2) could be true: what does it mean to discover a molecule if you don't know its structure? to me, the discovery of a molecule is precisely that - the discovery of its structure, since that's all that really distinguishes it from other molecules.
to me, (2) sounds a bit like saying that you remember how a song goes, but don't remember its lyrics or its melody. huh?

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finally - is there an answer choice that you think is better than (d)?