Question

Air has________ composition with________ oxygen at high attitudes.

• A. fixed, less
• B. variable, less
• C. variable, more
• D. fixed, more

Answer 1

The correct option is A fixed, less

Air has fixed composition with less oxygen at high altitudes. Air contains 78% nitrogen and 21% oxygen and less than 1% He, Ar, Ne and water vapour content.

This composition remains fixed at all locations but the oxygen becomes less dense at high altitudes so it is difficult to breathe in such low concentration of air.

Hence, option A is correct.