Logical Reasoning

PT137 · S2 · Q11 Scientists examined diamonds

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Scientists examined diamonds that were formed on Earth about 2.9 billion years ago.

Information

Diamonds, formed on Earth, about 2.9 billion years ago had a higher than normal concentration of sulfur-33.

causal (X can be explained only by Y)

chemical reactions ⇢ higher than normal stimulated by UV concent of sulfur-33

conditional (if = left side)

more than a trace not enough UV of oxygen in Earth's ⇢ to reach Earth's atmosphere 2.9 billion surface to stim chem reactions

Evaluate

Whenever we see a conditional on an Inference question, we ask ourselves two questions: 1. are there other conditionals here that could be chained up with this? 2. is there any fact that triggers this conditional (or more frequently, its contrapositive)?

Of the first three sentences, only the 3rd could seemingly be translated into a conditional. We would say,

higher than normal → chem reactions concentration of S-33 stim by UV

Whether we think of that 3rd sentence as a conditional chain or think of it as a causal fact, it definitely interacts with the last sentence, if we contrapose it:

enough UV light reached less than a Earth's surface to stim → trace of oxy chemical reactions in Earth's atmos

We know that sulfur-33's concentration was higher, which was caused by chemical reactions stimulated by UV. According to the contrapositive of this last sentence, this means that .

Goal

By applying the contrapositive of that last sentence to the facts presented before it, we derived that , so that's likely to be what the correct answer is testing.

But as always, we'll stay flexible and pick whichever answer we can best support.

11.

The information above most strongly supports which one of the following?

  1. Most diamonds with higher-than-normal concentrations

    Too Strong: most

    We can never infer anything about "Most X's" unless we had a fact about "Most X's". We were never told anything about "most diamonds with higher concentrations of sulfur-33", so we can't derive that most diamonds with that trait came from this era. This trap answer is a variation of the classic "only thing mentioned ? only thing". Because the passage only mentions high sulfur diamonds forming 2.9 billion years ago, this answer wants to trap us into thinking "the only time high sulfur diamonds formed was 2.9 billion years ago".

    2% picked this

  2. Ultraviolet light causes the oxygen

    Unsupported Causal Relationship

    We know that UV light stimulated some chemical reaction that led to the high-sulfur content of these diamonds. We have no way to say that this chemical reaction has anything to do with oxygen. This answer is just offering a Word Salad that invents a causal relationship between some of the wording in the last sentence and some of the wording from the previous sentences.

    6% picked this

  3. Correct

    Earth's atmosphere contained very little,

    Why this is right

    The final sentence tells us that, "If there was enough UV light to stimulate chemical reactions, then there was at most a trace a of oxygen in Earth's atmosphere 2.9 billion years ago." We know there was enough UV to stimulate chemical reactions, because we know that the high-sulfur diamonds were caused by chemical reactions stimulated by UV light. So we know that there was at most a trace of oxygen in Earth's atmosphere 2.9 billion years ago.

    Skill tested: Most Supported · how this choice captures the argument's function is the move to repeat next time.

    89% picked this

  4. Sulfur-33 is rarely found in

    Too Strong: rarely

    This essentially has the same problem as (A). Since the passage only mentioned sulfur-33 in diamonds that were formed 2.9 billion years ago, the test is trying to lure people into thinking "sulfur-33 only appeared in diamonds that were formed 2.9 billion years ago, so it rarely appears in diamonds since then". For all we know, all diamonds ever have sulfur-33 in them. The passage only told us that there are some diamonds from 2.9 billions years ago with more sulfur-33 than usual.

    1% picked this

  5. The formation of diamonds occurs

    Too Strong: only

    The passage doesn't give us any harsh rule that says "diamonds only form under this condition". It said "higher than normal concentrations of sulfur-33 only occur when chemical reactions are stimulated by UV light".

    2% picked this

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