Which of the Following Is True of Gases in the Heterosphere

Multiple Choice

Which of the following is true of gases in the heterosphere?

A) The hydrogen, helium, oxygen and nitrogen are well mixed.
B) The hydrogen and helium occur at the top of the heterosphere, and the nitrogen and oxygen at the bottom.
C) The nitrogen and oxygen occur at the top of the heterosphere and the hydrogen and helium at the bottom.
D) Nitrogen occurs at the top, followed-in descending order-by helium, oxygen and hydrogen.