Assertion : Coenzyme nicotinamide adenine dinucleotide (NAD) and NADP contain a vitamin.
Reason : The association of co-enzyme with apoenzyme is enduring .

Explanation

To solve the question, we need to analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that coenzymes nicotinamide adenine dinucleotide (NAD) and NADP contain a vitamin.
- It is known that NAD and NADP are derived from niacin, which is indeed a vitamin (Vitamin B3).
- Therefore, the assertion is **true**.

2. **Understanding the Reason**:
- The reason states that the association of coenzyme with apoenzyme is enduring.
- Coenzymes are typically transiently associated with their respective apoenzymes (the protein part of the enzyme).
- This means that they attach only temporarily during the catalytic process and do not have a long-lasting association.
- Therefore, the reason is **false**.

3. **Conclusion**:
- Since the assertion is true and the reason is false, we conclude that the assertion stands correct while the reason does not support the assertion.

### Final Answer:
- The assertion is true, and the reason is false.