Geologist: The dominant view that petroleum formed from the fossilized remains of plants and animals deep in the eart...

Andrew on July 17 at 03:35PM

Why not A?

The argument we are weakening relies on the presence of biomarkers as evidence that another theory is wrong. If answer choice A were true, then biomarkers would not be a reliable indicator of life which to me weakens the argument.

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Emil on July 19 at 09:33PM

The author here is refuting the idea that oil might have formed from inorganic carbon deposits, because we found bio markers, which are a sign of life, in oil.

To weaken this we would ideally want to show that bio markers also might show up in inorganic things, or somehow else got into the oil despite the oil not being organic.

A shows that not all organic things have biomarkers, which is different from saying that biomarkers can appear in inorganic things. If we had been told that some non fossil rocks had biomarkers that would be great, but the fact that they sometimes fail to appear wouldn't explain why they show up in a place we wouldn't want them.

I agree that A shows biomarkers aren't reliable, but it does so in the wrong direction. It shows that biomarkers are too weak to prove something is organic, when what we needed is that they are so strong that they can appear even when inorganic.

Andrew on July 20 at 04:28PM

Ah yea I see that. Thank you Emil.