The protein primarily involved in the maintenance of osmolarity of circulatory blood is

Options

A. Fibrogen
B. Prothombin
C. Albumin
D. Fibrin

Answer

To solve the question regarding the protein primarily involved in the maintenance of osmolarity of circulatory blood, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question asks for the specific protein that plays a key role in maintaining the osmolarity of blood. Osmolarity refers to the concentration of solutes in the blood, which is crucial for maintaining fluid balance.

2. **Identify the Options**: The options given are:
- A) Fibrinogen
- B) Prothrombin
- C) Albumin
- D) Fibrin

3. **Analyze Each Option**:
- **Fibrinogen**: This is a protein involved in blood clotting. It is converted to fibrin during the clotting process but does not play a role in osmolarity.
- **Prothrombin**: This is another clotting factor that is involved in the coagulation cascade. It does not contribute to osmolarity.
- **Albumin**: This is a major plasma protein that constitutes about 55% of the total blood protein. It is essential for maintaining osmotic pressure in the blood, thus playing a crucial role in osmolarity.
- **Fibrin**: This is the active form of fibrinogen and is also involved in blood clotting. It does not have a role in osmolarity.

4. **Select the Correct Answer**: Based on the analysis, the protein that primarily maintains the osmolarity of circulatory blood is **C) Albumin**.

5. **Conclusion**: The correct answer to the question is Albumin, as it is the protein that helps maintain the osmotic balance in the blood.