Indigenous Highlanders Living in the Andean Altiplano in South America

Indigenous highlanders living in the Andean Altiplano in South America, in the Tibetan plateau in Asia, and at the highest elevations of the Ethiopian highlands in East Africa have all adapted to living in an environment of oxygen-thin air. Researchers have found that

A) each population has evolved its own distinctly different biological adaptation to this environment.
B) these populations share the same mechanism of adaptation to hypoxic environments, proving that there was gene flow among these groups until very recently.
C) Andeans and Tibetans rely more on cultural means of adapting to hypoxic environments than highland Ethiopians do.
D) these populations illustrate humans' capacity to survive in extreme environments that have remained unchanged for more than 20,000 years.
E) cultural adaptations are more important than biological adaptations.