Question

In man, expired air contains oxygen about

• A. 4%
• B. 10%
• C. 16%
• D. 20%

Answer 1

The correct option is C 16%

Inhaled air contains more oxygen used to create energy and less carbon dioxide. Exhaled air which contains more carbon dioxide produced as a waste product of energy production and less oxygen as it has been used in respiration. Inhaled air contains 21% oxygen, 0.04% CO${}_2$ and 79% N${}_2$. Exhaled air contains 16% oxygen, 4% CO${}_2$ and 79% N${}_2$.

Therefore, the correct answer is option C.