PTB.S1.Q19

legaleezee

Hi,

This question has a 5-star difficulty but it looks like there's no explanation video on this.
What is everyone's thought process on this question. Here's my reasoning for why it comes down to C and D :

C. Some parts of the rock was under water, some part on land. Which one do we know is where the C-14 were found from (if its the unerwater part then it goes against the argument, if its the land part then it supports the argument). This is just not enough to know. This could go both ways. BUT it does cast doubt on the result of the study, how do you know which part of the rock you got your C-14 from.

D. Among the C-14 that were found in this rock, a small amount of C-14 come from the atmosphere. Meaning the rest of the C-14 can still come from remnants of plants and microbes. Doesn't weaken the argument much, but it cast doubt.

I picked D but the correct answer is C. Can someone explain their thought process and why C is a better ac?

claremont

I suspect you're having difficulty analyzing it because... AC D is the correct answer, not C.

I also narrowed it down to AC C and AC D.

AC C helps because it shows that the necessary condition that the paleontologist is arguing for was met. It would be devastating to their argument if it was shown that those 1.2-billion-year-old rocks were always submerged underwater.

AC D, "carbon 14 ... entered the soil directly from the atmosphere" basically says that biological activity isn't necessary for carbon 14 to have entered the rocks. If that's the case then using those rocks as evidence of biological activity on earth isn't as persuasive.

Anyway, that's my thinking.