Blood clotting requires

Options

A. `Na^(+)` and `K^(+)`
B. `Na^(+)` and prothrombin
C. `Na^(+)` and thromboplastin
D. `Ca^(2+)` and thromboplastin .

Answer

### Step-by-Step Solution:

1. **Understanding Blood Clotting**: Blood clotting, also known as coagulation, is a complex process that prevents excessive bleeding when a blood vessel is injured.

2. **Key Components Required for Blood Clotting**:
- **Thromboplastin**: This is a plasma protein that plays a crucial role in the clotting process. It initiates the clotting cascade.
- **Thrombin**: An enzyme that converts prothrombin (an inactive precursor) into thrombin, which is essential for the formation of fibrin, a protein that helps form the blood clot.
- **Calcium Ions (Ca²⁺)**: These ions are vital for several steps in the clotting cascade, acting as a cofactor for various clotting factors.

3. **Other Factors**: Several clotting factors (such as factor V, VI, VIII, IX, and XII) are also involved in the coagulation process, but they are not mentioned in the question.

4. **Elimination of Incorrect Options**:
- Sodium and potassium are not directly involved in the blood clotting process, so any options including them can be eliminated.

5. **Conclusion**: The correct answer is that blood clotting requires calcium ions and thromboplastin.