Linguist Dr. Kenji Yamamoto studied bilingual children in multilingual households over a five-year period. He found that children who regularly switched between two languages in conversation performed better on tasks requiring mental flexibility, such as sorting objects by changing rules. Yamamoto noted that this advantage appeared regardless of which specific languages the children spoke, suggesting that the cognitive benefit comes from the act of managing two language systems rather than from features of any particular language.

Which choice best states the main idea of the text?

The golden poison frog of Colombia is widely considered the most toxic animal on Earth. A single frog carries enough poison to be lethal to several adult humans, yet it produces none of this toxin on its own. Research has shown that the frogs acquire their poison from the insects they eat in the wild. When raised in captivity on a different diet, golden poison frogs gradually become harmless.

Which detail from the text most directly supports the idea that the frog’s toxicity depends on its environment?

Urban heat islands occur when cities experience significantly higher temperatures than surrounding rural areas. Buildings, roads, and other infrastructure absorb and retain heat during the day and release it slowly at night, preventing temperatures from dropping as much as they would in less developed areas. Researchers at the University of Wisconsin found that cities with more tree canopy coverage showed measurably lower heat island effects, with some neighborhoods experiencing temperatures up to 5 degrees Celsius cooler than nearby treeless districts.

Based on the text, what is the most likely reason tree canopy coverage reduces the urban heat island effect?

In a 2021 study, marine biologist Dr. Elena Vargas tracked the migration patterns of leatherback sea turtles across the Atlantic Ocean. She discovered that the turtles did not follow a single predictable route but instead adjusted their paths in response to shifting ocean currents and water temperatures. Vargas concluded that leatherbacks rely on real-time environmental cues rather than fixed internal maps to navigate their long migrations.

Which choice best states the main idea of the text?