June 2017 LSAT Section 3 Question 24

After a nuclear power plant accident, researchers found radioactive isotopes of iodine, tellurium, and cesium- but no...

devon on June 10, 2022

Why eliminate fuel rods?

I'm a little confused about the question explanation and how it rules out fuel rods. (I might be misreading something and sorry if I am.) That fuel rods do not contain an element that must be accounted for does not strike me as a particularly convincing reason to rule it out as a contributor in this instance, only as the lone contributor. Also, it does not seem like there must be a single explanation, unless the disjunction acts as exclusionary here. I.e. If x,y,z were found and could only be a product of P or Q, while P produces x and y (not z) and Q can indirectly produce all three; the only valid deduction seems to be that P alone is not responsible. (right?)

Replies

Create a free account to read and take part in forum discussions.

Already have an account? log in

jakennedy on June 12, 2022

Hi Devon,

Most of what you said is exactly correct. It is quite possible that both the fuel rods and the plant’s core both contributed to the material detected by the researchers. Indeed, the stimulus does not even preclude the fuel rods from having some tellurium isotopes, stating, “fuel rods never contain significant quantities of tellurium”.

Therefore, the correct answer choice does not necessarily have to be true. This leads to the logical question: how is an answer choice that does not necessarily have to be true correct on a Must be True question?

The key is how they phrased the question stem itself. In some cases, must be true questions will use language like “must be true” or “can be properly inferred”, but on this question the stem says “most strongly supported”. That is, the logical force of our question stem is slightly weaker than in the other cases. We will generally approach it the same way as we would on any other must be true question, but we may be able to come up with some loopholes that would disprove the correct answer choice.

On this specific question, the author provides three possible explanations for a phenomenon.

1 The material came from the fuel rods.
2 The material came directly from the plant’s core.
3 The material came from the steam that had contact with the core.

Option 1 is at best a partial explanation because it cannot explain the presence of tellurium.

Option 2 is very unlikely because we would expect the researchers to have detected the heavy isotopes.

Option 3, however, seems perfectly sufficient to cause the phenomenon.

So in short, it is possible that some of the material came from the fuel rods, but the passage does not give much support for that hypothesis. Rather, the stimulus is structured to prove that the steam is the cause. If the question stem had said “must be true” I would be hesitant to select answer choice B, but since it says “most strongly supported” you can select it without reservation.

devon on June 28, 2022

Ahhhhh, I see. Thank you very much!