Assertion `:-` Prothrombinase enzymes converts prothrombin into active thrombin.
Reason`:` Thromboplastin react with plasma protein in the presence of `Ca^(+2)` ions to form prothrombinase.

Options

A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion .
B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion
C. If Assertion is True but the Reason is False.
D. If both Assertion & Reason are false.

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Prothrombinase enzymes convert prothrombin into active thrombin."
- This statement is **true**. Prothrombinase is an enzyme complex that catalyzes the conversion of prothrombin (an inactive precursor) into thrombin (the active form).

2. **Understanding the Reason**:
- The reason states that "Thromboplastin reacts with plasma protein in the presence of Ca²⁺ ions to form prothrombinase."
- This statement is also **true**. Thromboplastin (also known as tissue factor) interacts with plasma proteins and calcium ions to form the prothrombinase complex necessary for the conversion of prothrombin to thrombin.

3. **Evaluating the Relationship**:
- Although both the assertion and reason are true, we need to determine if the reason correctly explains the assertion.
- The assertion is about the conversion of prothrombin to thrombin, while the reason describes the formation of prothrombinase. The reason does not directly explain why prothrombin is converted to thrombin; rather, it explains how prothrombinase is formed.

4. **Conclusion**:
- Since both statements are true, but the reason does not provide a correct explanation for the assertion, the correct option is that both the assertion and reason are true, but the reason is not a correct explanation of the assertion.

### Final Answer:
Both assertion and reason are true, but the reason is not a correct explanation of the assertion.