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The atmosphere contains the following gases:
  • A
    78% nitrogen, 21% oxygen, 0.03% carbon dioxide, rest: rare gases.
  • B
    78% helium, 21% oxygen, 1% carbon monoxide, rest: rare gases.
  • C
    78% helium, 21% oxygen, 0.03% carbon dioxide, rest: rare gases.
  • D
    78% oxygen, 21% nitrogen, 1% carbon monoxide, rest: rare gases.

Composition of the Atmosphere

The atmosphere contains about 21% of oxygen. The other gases in the air are nitrogen, about 78%, and small amounts of carbon dioxide, water vapour and the rare gases such as argon. These volume percentages for each gases remain constant to about 70 000 ft - well within the altitudes at which conventional aircraft operate.

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