Which of the following statements are correct ?
(i) `Ca^(+2)` is necessary for blood coagulation
(ii) Coagulation in blood vessel is prevented during normal condition by heparin
(iii) Clotting of blood involves changes of fibrinogen to fibrin by thrombin
(iv) Blood clotting involves casecading process involving a number of factors present always in the active form.

Options

A. (i),(iii) and (iv)
B. (ii) and (iv)
C. (i),(ii) and (iii)
D. (iii) and (iv)

Explanation

To determine which of the statements regarding blood coagulation are correct, let's analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement (i): `Ca^(+2)` is necessary for blood coagulation.**
- Calcium ions (`Ca^(+2)`) play a crucial role in the blood coagulation process. They are essential for the activation of various clotting factors and for the conversion of prothrombin to thrombin, which is necessary for the formation of fibrin from fibrinogen.
- **Conclusion:** This statement is **true**.

2. **Statement (ii): Coagulation in blood vessels is prevented during normal conditions by heparin.**
- Heparin is an anticoagulant that is naturally present in the body, particularly secreted by mast cells. It helps to prevent the formation of blood clots in normal conditions by inhibiting certain clotting factors.
- **Conclusion:** This statement is **true**.

3. **Statement (iii): Clotting of blood involves changes of fibrinogen to fibrin by thrombin.**
- Fibrinogen is a soluble plasma protein that is converted into insoluble fibrin by the enzyme thrombin during the clotting process. This conversion is a key step in the formation of a blood clot.
- **Conclusion:** This statement is **true**.

4. **Statement (iv): Blood clotting involves a cascading process involving a number of factors present always in the active form.**
- This statement is incorrect because the clotting factors are typically present in an inactive form in the bloodstream. They are activated in a cascade manner only when needed for clotting, preventing unnecessary clot formation in normal blood flow.
- **Conclusion:** This statement is **false**.

### Final Answer:
The correct statements are (i), (ii), and (iii). Therefore, the answer is option C.

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