$ "A" DNA contains eleven base pairs.
! "Z" DNA contains only nine base pairs.

Options

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

Answer

To solve the question regarding the assertions about A-DNA and Z-DNA, we will analyze each assertion step by step.

### Step 1: Analyze Assertion about A-DNA
- **Assertion**: A-DNA contains 11 base pairs.
- **Explanation**: A-DNA is one of the forms of DNA. It is a right-handed double helix and is known to have a specific structure that includes a certain number of base pairs per helical turn. The assertion states that A-DNA contains 11 base pairs, which is correct based on our understanding of A-DNA structure.

### Step 2: Analyze Reasoning about Z-DNA
- **Reason**: Z-DNA contains only 9 base pairs.
- **Explanation**: Z-DNA is another form of DNA that has a left-handed helical structure. The number of base pairs in Z-DNA is typically more than what is stated in the assertion. In fact, Z-DNA generally has around 12 base pairs per helical turn, not 9. Therefore, the statement that Z-DNA contains only 9 base pairs is incorrect.

### Step 3: Conclusion
- Based on the analysis:
- The assertion that A-DNA contains 11 base pairs is correct.
- The reason that Z-DNA contains only 9 base pairs is incorrect.
- Therefore, the correct option is that the assertion is correct, but the reason is wrong.

### Final Answer:
The correct option is that the assertion is correct and the reason is incorrect.

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