Q
What is exhaled in human respiration?
RRB NTPC (Stage-I)
05/04/2016 (Shift-III)
2016
✓ Answer:
D
Carbon dioxide
The source key selects carbon dioxide as the respiratory waste gas. Exhaled air is actually a mixture containing nitrogen, oxygen, carbon dioxide and water vapour, so option A is also scientifically valid under this wording.