Assertion; DNA replication is semiconservative.
Reason; Helicases are the enzymes which can break the hydrogen bonds between the nuclotides of DNA

Options

A. If both A and R are correct and R is correct explanation of A
B. If both A and R are correct but R is not correct explanation of A
C. If A is correct, R is wrong
D. If both A and R are wrong.

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "DNA replication is semiconservative."
- This means that during DNA replication, each new double-stranded DNA molecule consists of one original (template) strand and one newly synthesized strand.

2. **Evaluating the Assertion**:
- This is a well-established fact in molecular biology. When DNA replicates, the two strands of the double helix separate, and each serves as a template for the formation of a new complementary strand.
- Therefore, the assertion is **correct**.

3. **Understanding the Reason**:
- The reason provided states that "Helicases are the enzymes which can break the hydrogen bonds between the nucleotides of DNA."
- Helicases are indeed enzymes that play a crucial role in DNA replication by unwinding the DNA double helix.

4. **Evaluating the Reason**:
- Helicases do break the hydrogen bonds between the base pairs of the DNA strands, allowing the two strands to separate.
- This is essential for the replication process, as it allows each strand to be copied.
- Therefore, the reason is also **correct**.

5. **Determining the Relationship Between Assertion and Reason**:
- While both the assertion and the reason are correct, the reason does not directly explain the assertion.
- The assertion is about the semiconservative nature of DNA replication, while the reason describes the function of helicases in the process.

6. **Conclusion**:
- Since both the assertion and the reason are correct but the reason does not explain the assertion, the correct option is: **Both A and R are correct, but R is not the correct explanation of A.**