Question 9·200 Super-Hard SAT Reading Questions·Information and Ideas

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When offspring of metal-tolerant bentgrass from abandoned copper mines remain tolerant in uncontaminated common gardens, researchers often interpret this persistence as evidence of genetic adaptation. Yet seed-associated microbes can pass from parent plants to seedlings. Leena Patel and colleagues found that untreated seeds from mine populations yielded seedlings with much greater copper tolerance than seeds from nearby nonmine populations. Surface sterilizing mine seeds substantially reduced, but did not erase, this advantage. Conversely, inoculating sterilized nonmine seeds with bacterial strains cultured from mine seeds increased tolerance, though not to the level of untreated mine seeds. Genome scans also identified differences between the populations near metal-transport genes, but the researchers did not determine whether these variants affected tolerance. Taken together, the findings suggest that _____

Which choice most logically completes the text?

For inference questions involving experiments, track what each intervention changes and how complete its effect is. Favor the choice that combines all relevant findings while preserving the study's uncertainty; reject choices that claim a factor is sufficient, necessary, or interactive when the evidence establishes only a partial contribution.

Hints

Hint 1
Compare both experiments
Consider what happened when microbes were removed from mine seeds and when microbes were added to nonmine seeds.
Hint 2
Focus on degree
Pay attention to the phrases “substantially reduced, but did not erase” and “not to the level.” Avoid a conclusion that treats the microbial effect as either nonexistent or complete.
Hint 3
Avoid proving more than the study shows
Finding evidence for two possible influences does not necessarily establish how those influences relate to each other.

Step-by-step

Step 1
Identify the evidence for a microbial contribution
Sterilizing mine seeds substantially reduced their seedlings' tolerance, while adding bacteria from mine seeds increased tolerance in nonmine seedlings. Together, these results support a role for seed-associated microbes.
Step 2
Notice the limits of that explanation
Sterilization did not erase the mine seedlings' advantage, and inoculation did not raise nonmine seedlings to the untreated mine seedlings' level. Therefore, the microbes tested do not fully explain the difference.
Step 3
Evaluate the remaining possibility cautiously
The genome scans found population differences near relevant genes, but those variants were not tested. Genetic adaptation remains possible, but the evidence does not establish it as the explanation for the residual advantage.

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SAT Reading: Information and IdeasAdvancedCoreInferences about a study

Question 9·200 Super-Hard SAT Reading Questions·Information and Ideas

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