Question 372, Meteorology - PPL(H) - Private Pilot License

Oxygen 21 % Water vapour 78 % Noble gases / carbon dioxide 1 %
Oxygen 21 % Nitrogen 78 % Noble gases / carbon dioxide 1 %
Oxygen 78 % Water vapour 21 % Nitrogen 1 %
Nitrogen 21 % Oxygen 78 % Noble gases / carbon dioxide 1 %