the haemoglobin of a human foetus

Options

A. Has higher affinity for oxygen than that of an adult
B. Has a lower affinity for oxygen than that of the adult
C. Its affinity for oxygen is the same as that of adult
D. Has two protein sub-units instead of four

Answer

### Step-by-Step Solution:

1. **Understanding Fetal Hemoglobin**:
- Fetal hemoglobin (HbF) is the type of hemoglobin found in the human fetus. It differs from adult hemoglobin (HbA) in its structure and function.

2. **Oxygen Affinity**:
- Fetal hemoglobin has a higher affinity for oxygen compared to adult hemoglobin. This means that HbF can bind oxygen more effectively, even at lower concentrations of oxygen.

3. **Physiological Context**:
- During pregnancy, the fetus receives oxygen from the mother’s blood through the placenta. The oxygen concentration in the mother’s blood is lower than in the air, which necessitates that fetal hemoglobin be more efficient at capturing oxygen.

4. **Conclusion**:
- Because of its higher affinity for oxygen, fetal hemoglobin is crucial for ensuring that the fetus receives enough oxygen for development while in the womb.

5. **Correct Answer**:
- Therefore, the correct statement regarding the hemoglobin of a human fetus is that it has a higher affinity for oxygen than that of adults.