Donnan's membrane is the 

Options

A. Respiratory membrane
B. Filtration membrane of Bowman's
C. Plasma membrane of erythrocytes
D. Plasma membrane of WBC

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about Donnan's membrane and provides multiple-choice options. We need to identify which option correctly describes Donnan's membrane.

2. **Analyzing the Options**:
- **Respiratory Membrane**: This is associated with the alveoli in the lungs and is not related to Donnan's membrane.
- **Filtration Membrane of Bowman's Capsule**: This membrane is part of the nephron in the kidneys, involved in the filtration of blood, but it is not referred to as Donnan's membrane.
- **Plasma Membrane of Erythrocytes**: Erythrocytes are red blood cells, and their plasma membrane is indeed known as Donnan's membrane due to its role in maintaining the ionic balance and osmotic pressure.
- **Plasma Membrane of WBC**: White blood cells (WBCs) have their own plasma membranes, but they are not referred to as Donnan's membrane.

3. **Identifying the Correct Answer**: Based on the analysis, the plasma membrane of erythrocytes is the correct answer, as it is specifically known as Donnan's membrane.

4. **Conclusion**: Therefore, the answer to the question is the plasma membrane of erythrocytes.

**Final Answer**: Donnan's membrane is the plasma membrane of erythrocytes.

---