SAT Reading and Writing: North American Mercury Hypothesis Inference
A hard Digital SAT inference question. Studies in Sweden and elsewhere match the North American mercury–DOC pattern; what does that suggest about the “particular to North America” hypothesis?
Question
Many studies have found a positive association between levels of dissolved organic carbon and mercury in bodies of fresh water in North America. But Petri Porvari and Matti Verta did not find this correlation in a study conducted in Finland, leading some scientists to hypothesize that the association is particular to North America. However, several other studies conducted outside North America, such as one by Sara M. Ekström and colleagues in Sweden, showed similar results to the North American studies, while few have produced results similar to those of Porvari and Verta’s study, suggesting that ______
Which choice most logically completes the text?
Step-by-Step Solution
Pin down the hypothesis, then follow the weight of the evidence.
1State the hypothesis exactly.
A positive association between dissolved organic carbon (DOC) and mercury appears in North American fresh water. Porvari and Verta did not see the same pattern in Finland — a single contrary result.
On the basis of that one Finnish study, some scientists proposed a specific hypothesis: the DOC–mercury association is particular to North America. The strong claim here is that the association does not appear outside North America.
2Weigh the new evidence against that claim.
The passage then introduces “several other studies conducted outside North America” — including Ekström in Sweden — which “showed similar results to the North American studies.”
It also notes that “few have produced results similar to those of Porvari and Verta’s study.” In other words, the Finnish study is the outlier; the majority of non–North American studies match the North American pattern.
If the association were truly particular to North America, you would expect non–North American studies to consistently fail to find it — the opposite of what the evidence shows.
3Draw the inference that the evidence forces.
Because the non–North American evidence largely behaves like the North American evidence, the hypothesis that the association is unique to North America is no longer well supported.
The most logical completion of the sentence is that the hypothesis is likely incorrect.
4Eliminate the distractors.
A reverses the logic — the bulk of the new evidence contradicts the hypothesis, so the hypothesis is not “correct.”
B introduces specific claims about how high DOC and mercury levels are in Finland; the passage never compares concentrations.
C invents methodological problems for Ekström’s study; the passage gives no hint that the Sweden measurements were flawed.
D is the only option supported by the passage. The answer is D.