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.