Assertion (A) : Rosie was the first transgenic cow.
Reason (R): It contained human alpha lactalbumin.

Options

A. Both assertion (A) and reason (R ) are true and reason (R ) is the correct explanation of assertion (A ) .
B. Both assertion (A) and reason ( R) are true but reason (R ) is not the correct explaination of assertion (A ) .
C. Assertion (A) is true but reason (R ) is false .
D. Assertion (A ) is false but reason (R ) is true.

Explanation

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**: The assertion states that "Rosie was the first transgenic cow."
- A transgenic cow is one whose genetic material has been altered through genetic engineering. Rosie is indeed recognized as the first transgenic cow created by scientists.

2. **Understanding the Reason (R)**: The reason states that "It contained human alpha-lactalbumin."
- Alpha-lactalbumin is a protein found in human milk. In the case of Rosie, scientists inserted the gene responsible for producing this protein into her genome, allowing her to produce milk enriched with human alpha-lactalbumin.

3. **Evaluating the Truth of Both Statements**:
- Both the assertion and the reason are true. Rosie is the first transgenic cow, and she was engineered to produce milk containing human alpha-lactalbumin.

4. **Analyzing the Relationship Between A and R**:
- While both statements are true, the reason provided does not serve as a correct explanation for the assertion. The assertion is about Rosie being the first transgenic cow, while the reason discusses the specific protein she produces. The fact that she produces human alpha-lactalbumin does not explain why she is considered the first transgenic cow.

5. **Conclusion**:
- The correct answer is: Both assertion (A) and reason (R) are true, but reason (R) is not the correct explanation for assertion (A).

### Final Answer:
Both assertion (A) and reason (R) are true, but reason (R) is not the correct explanation for assertion (A).