A : Cofactor of an enzyme may be a prosthetic group.
R : NAD derived from niacin is a co-enzyme.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1).
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2).
C. If Assertion is true statements but Reason is false, then mark (3).
D. If both Assertion and Reason are false statements, then mark (4)

Answer

To analyze the assertion and reason provided in the question, we can break down the information as follows:

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states: "A cofactor of an enzyme may be a prosthetic group."
- A cofactor is a non-protein chemical compound that is required for the biological activity of an enzyme.
- Cofactors can be divided into two categories:
- **Coenzymes**: These are organic molecules that bind to the enzyme temporarily and assist in enzyme activity.
- **Prosthetic groups**: These are tightly bound to the enzyme and are often required for the enzyme's activity.

2. **Evaluating the Assertion**:
- The assertion is true because a cofactor can indeed be a prosthetic group. Prosthetic groups are a type of cofactor that are permanently attached to the enzyme.

3. **Understanding the Reason**:
- The reason states: "NAD derived from niacin is a coenzyme."
- NAD (Nicotinamide adenine dinucleotide) is indeed derived from niacin (vitamin B3) and functions as a coenzyme in various biochemical reactions, particularly in redox reactions.

4. **Evaluating the Reason**:
- The reason is also true because NAD acts as a coenzyme that assists enzymes in catalyzing reactions.

5. **Conclusion**:
- Both the assertion and the reason are true.
- However, the reason does not serve as a correct explanation for the assertion. The assertion discusses cofactors in general, while the reason specifically addresses coenzymes, which are a subset of cofactors.

### Final Answer:
- Both the assertion and the reason are true, but the reason is not the correct explanation for the assertion. Therefore, the correct option is that both are true, but the reason is not the correct explanation.