[A] : Vitamin K is water soluble and must for fibrin production.
[R]: It catalyses the conversion of fibrin into fibrinogen.

Options

A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false

Answer

To solve the assertion-reason question regarding Vitamin K, we will analyze both the assertion and the reason step by step.

### Step 1: Analyze the Assertion
The assertion states: "Vitamin K is water soluble and must for fibrin production."

- **Fact Check**: Vitamin K is actually a fat-soluble vitamin, not water-soluble. It plays a crucial role in the synthesis of certain proteins required for blood coagulation, which includes the conversion of fibrinogen to fibrin.

### Conclusion for Step 1:
The assertion is **false** because Vitamin K is fat-soluble, not water-soluble.

### Step 2: Analyze the Reason
The reason states: "It catalyzes the conversion of fibrin into fibrinogen."

- **Fact Check**: This statement is incorrect. The correct process is that fibrinogen (the inactive form) is converted into fibrin (the active form) by the enzyme thrombin. Vitamin K does not directly catalyze this conversion; instead, it is involved in the post-translational modification of clotting factors that are necessary for the clotting process.

### Conclusion for Step 2:
The reason is also **false** because it inaccurately describes the conversion process.

### Final Conclusion:
Since both the assertion and the reason are false, the correct answer is that both the assertion and reason are false.

### Answer:
Both assertion and reason are false.

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