UPTET Paper 1 2013 Solved Paper

Concept:The atmosphere is a mixture of gases. Nitrogen and oxygen together account for about 99% of its volume.Explanation:By volume, the permanent gases in the atmosphere are: nitrogen ($N_2$) ≈ 78%, oxygen ($O_2$) ≈ 21%, and others (argon, carbon dioxide, etc.) about 1%.Adding nitrogen and oxygen gives 78% + 21% = 99%.Thus, these two gases make up the vast majority of the atmosphere.Ozone ($O_3$) is a trace gas found mainly in the stratosphere and does not contribute significantly to the 99%.Answer:Option B: Oxygen and Nitrogen