Assertion: Replication of DNA is perfect.
Reason: Defect in DNA spoils the DNA.

Options

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

Answer

### Step-by-Step Solution

1. **Understanding the Assertion**: The assertion states that "Replication of DNA is perfect."
- While DNA replication is highly accurate, it is not entirely perfect. There are mechanisms in place that minimize errors, but mistakes can still occur.

2. **Analyzing the Accuracy of DNA Replication**:
- DNA replication is a process that involves multiple enzymes and mechanisms, ensuring high fidelity. On average, there is about one mistake for every 10 billion nucleotides replicated. This high accuracy leads to the perception that replication is "perfect."

3. **Understanding the Reason**: The reason states that "Defect in DNA spoils the DNA."
- This statement implies that any defect or error in DNA replication leads to spoilage or damage to the DNA. While defects can lead to mutations, not all errors result in detrimental effects on the organism.

4. **Evaluating the Relationship Between Assertion and Reason**:
- The assertion is true in the context of high accuracy, but it is not perfect due to the possibility of errors. The reason, however, is misleading because not every defect spoils DNA; some may not have significant consequences.

5. **Conclusion**:
- Since the assertion is true (DNA replication is highly accurate) and the reason is false (not all defects spoil DNA), the correct answer is: "If the assertion is true, the reason is false."