Prompt: Which one of the following can most reasonably be concluded on the basis of the researchers’ findings?
Difficulty: 🌕🌕🌕🌑
How will the right answer fit in terms of support and conclusion?
Only the right answer will be a conclusion supported by the passage.
Highlight the main conclusion in the passage, if there is one:
There is no conclusion in the passage. The right answer will be the conclusion.
[BACKGROUND]. [SUPPORT].
This passage is screaming cause-and-effect at you. Did you hear it? The main support is a correlation between flouride and sodium concentrations in the groundwater. And the author said that “other relevant variables are held constant”, which totally foreshadows a conclusion that the the sodium causes a higher concentration of flouride somehow.
Map the wording of the answers to the wording of the passage:
(A) …not the primary source of flouride…
Only one source of flouride is mentioned or referenced in the passage, so no way you’re making a conclusion about what the “primary” source is.
(B) Rainfall does not affect flouride concentrations…
Liar! The first sentence explains the exact opposite, so no way this is a valid conclusion.
(C) Sodium-bearing minerals dissolve at a faster rate…
Where do you see anything about the speed at which these minerals dissolve? Where do you see anything about “sodium-bearing minerals”? Me neither. This comparison is way out of left field and definitely not supported by the passage.
(D) Sodium in groundwater increases the rate at which flouride-bearing minerals dissolve.
Boom! The LSAT can use a lot of different wording to say one thing causes another, and “increases” is one of them for sure. This is exactly the cause-and-effect relationship the passage sets up with its correlation info.
(E) …also contains…
That’s just saying there’s a correlation again, but it does nothing to explain the “significantly higher” flouride when sodium is around versus when it isn’t. If you’re trained on recognizing correlation vs. cause-and-effect, this is an easy elimination.
(D) is the correct answer.
Common pattern/s in this question: The LSAT thinks this is a hard one, and it probably is for folks who don’t recognize that support about a correlation is very likely to lead to a conclusion about cause-and-effect.
Elliot Hirsen / LSAT coach 
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