Which row indicates the composition of expired air from a healthy person?
- Acarbon dioxide $0.04\%$; oxygen $21\%$; water vapour: saturated
- Bcarbon dioxide $0.04\%$; oxygen $16\%$; water vapour: variable
- Ccarbon dioxide $4\%$; oxygen $21\%$; water vapour: variable
- Dcarbon dioxide $4\%$; oxygen $16\%$; water vapour: saturated