Assertion :- Complementary base pairing confers a very unique property to the DNA chains.
Reason : If sequence of one strand is known then sequence in other strand can be predicted.

Options

A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion.
B. If both Assertion & Reason are trur 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 "Complementary base pairing confers a very unique property to the DNA chains." This means that the way bases pair with each other in DNA (adenine with thymine and cytosine with guanine) gives DNA its unique structure and function.

2. **Understanding the Reason**: The reason provided is "If the sequence of one strand is known then the sequence in the other strand can be predicted." This is a direct consequence of the complementary nature of the base pairing in DNA. If you know one strand, you can determine the other strand because of the specific pairing rules.

3. **Evaluating the Truth of the Assertion**: The assertion is true. Complementary base pairing is indeed a unique property of DNA that allows it to maintain its double helix structure and ensures accurate replication and transcription.

4. **Evaluating the Truth of the Reason**: The reason is also true. Knowing the sequence of one strand allows for the prediction of the sequence of the complementary strand due to the specific base pairing rules (A pairs with T, and C pairs with G).

5. **Determining the Relationship**: The reason is a correct explanation of the assertion. The unique property of DNA (assertion) is that it allows for the prediction of one strand's sequence from the other (reason).

6. **Conclusion**: Both the assertion and the reason are true, and the reason correctly explains the assertion. Therefore, the correct answer is that both assertion and reason are true, and the reason is the correct explanation of the assertion.

### Final Answer:
**Option A**: Both assertion and reason are true, and reason is the correct explanation of assertion.

---