Assertion. Guanine cannot pair with cytosine.
Reason. Guanine and cytosine do not have perfect matching.

Options

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

Answer

**Step-by-Step Solution:**

1. **Understanding the Assertion**: The assertion states that "Guanine cannot pair with Cytosine." This is a statement about the base pairing rules in DNA.

2. **Base Pairing Rules**: In DNA, the base pairing rules dictate that specific nitrogenous bases pair with each other. Adenine (A) pairs with Thymine (T), and Guanine (G) pairs with Cytosine (C).

3. **Evaluating the Assertion**: Since Guanine (G) can indeed pair with Cytosine (C), the assertion is incorrect.

4. **Understanding the Reason**: The reason given is that "Guanine and Cytosine do not have perfect matching." This suggests that there is some issue with the pairing between these two bases.

5. **Evaluating the Reason**: Guanine and Cytosine form a stable pair through three hydrogen bonds, which is considered a strong pairing. Therefore, the reason is also incorrect.

6. **Conclusion**: Both the assertion and the reason are false. Guanine does pair with Cytosine, and they have a strong and stable pairing due to the presence of three hydrogen bonds.

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