Question

Which of the following differentiates the expired air from the inspired air?

• A. Less oxygen
• B. Presence of bacteria
• C. More water vapour
• D. All of the above

Answer 1

The correct option is D All of the above

• Inhaled air: ≈≈ 77% nitrogen, ≈≈ 21% oxygen, ≈≈ 1% argon, ≈≈ 0.04% carbon dioxide (plus some water vapor, traces of other gases)
• Exhaled air: ≈≈ 77% nitrogen, ≈≈ 14% oxygen, ≈≈ 4% carbon dioxide, ≈≈4% water vapor, ≈≈ 1% argon (plus traces of other gases)

So, the correct option is 'All of the above'.