Which reactions occur within a capillary in an alveolus? 1. carbon dioxide + water $\rightarrow$ carbonic acid 2. carbon dioxide + haemoglobin $\rightarrow$ carbaminohaemoglobin 3. haemoglobinic acid $\rightarrow$ haemoglobin + hydrogen ions 4. hydrogencarbonate ions + hydrogen ions $\rightarrow$ carbon dioxide + water
- A1 and 2
- B3 and 4
- C3 only
- D4 only