SAT OwlQuestion bank / Central Ideas and Details
For decades, researchers assumed that the human gut microbiome, the community of microbes living in the digestive tract, was largely fixed by early adulthood. A long-term study led by microbiologist Daniel Okoye complicates that assumption. Tracking 300 adults over ten years, Okoye's team found that the overall diversity of each person's microbiome stayed fairly steady, but the particular species present shifted considerably, especially after changes in diet or travel abroad. Stability at one level, the team concluded, can mask substantial turnover at another.
Which choice best states the main idea of the text?
Okoye's study shows that the diversity of the gut microbiome declines steadily with age.
Okoye's study identifies travel abroad as the main cause of changes in the gut microbiome.
Okoye's study confirms that the gut microbiome becomes fixed by early adulthood.
Okoye's study found that although overall microbiome diversity was stable, the specific species present changed substantially over time.
Show answer and explanation
Answer: D
The study's key finding has two parts: diversity stayed steady, but the species making up the microbiome changed a lot. The final sentence sums this up as stability at one level hiding turnover at another. Choice D captures both parts.
Choice B treats one example as the main cause; travel is mentioned along with diet as a situation in which shifts were especially noticeable.
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