An astronomer studying planets outside our solar system has analyzed the atmospheres of four planets. Which of these planets’ at
mospheres would be most able to support a colony of humans? Planet C: 78% Nitrogen, 1% Oxygen, 21% Other Planet B: 82% Nitrogen, 11% Oxygen, 7% Other Planet A: 76% Nitrogen, 23% Oxygen, 1% Other Planet D: 27% Nitrogen, 3% Oxygen, 70% Other
