Q11 - Scientists examined diamonds

[samuelfbaron]

I was wondering if I could get some input on this question.

Although I got the answer correct, I was a little confused a certain statement within the correct answer (C).

If earth's atmosphere contains 'very little' then how can (C) be the correct answer? The stimulus states that if there is more than a trace of oxygen in the atmosphere then the chemical reaction would not occur. Does the 'if any' clause allow for (C) to be the correct answer?

[rinagoldfield]

Hi S.F.Baron,

(C) offers a rock-solid (diamond-hard?) inference from the information given in the stimulus.

Here’s what we know:

1. The diamonds formed 2.9 billion years ago on Earth.
2. Only UV light could have stimulated the diamonds’ sulfur-33 concentration.
3. If there had been more than a trace amount of oxygen in the Earth’s atmosphere, UV light could not have reached earth to stimulate the sulfur-33 concentration.

We know the diamonds formed. Therefore, the Earth’s atmosphere 2.9 billion years ago must have contained "a trace amount" or less of oxygen. In other words, the atmosphere could have supported a hint of oxygen, but no more.

(C) tells us that little, if any, oxygen was present in the Earth’s atmosphere 2.9 billion years ago. The phrase "little, if any" perfectly matches the phrase "no more than a trace amount." This is a good inference.

(A) , (D), and (E) all talk about diamonds in general, or diamonds formed more recently than 2.9 billion years ago. But we only know about these specific diamonds. These are bad inferences.

(B) is tempting... but UV rays caused chemicals reactions in the diamonds, not the atmosphere.

[BillP]

I was unsure how to eliminate A, though I did sense that it was not the correct answer.

Later I would see that the stimulus says nothing about whether, for example, "all" of the mentioned diamonds were formed 2.9 million years ago. The stimulus merely says that the scientists examined diamonds that were formed 2.9 million years ago, leaving it open as to whether or not, for example, "all" such diamonds were formed 2.9 million years ago.

Thus, A would be incorrect since the stimulus never states (or suggests) what A states.