Assertion (A) : The fusion of sperm and ovum to form zygote is called fertilization.
Reason (R): It occurs at ampullary isthmic junction of the fallopian tube

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 explanation 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:**
- The assertion states that the fusion of sperm and ovum to form a zygote is called fertilization.
- This is correct because fertilization is defined as the process where a male gamete (sperm) and a female gamete (ovum) combine to form a diploid zygote.

2. **Understanding the Reason:**
- The reason given is that fertilization occurs at the ampullary-isthmic junction of the fallopian tube.
- This is also correct; fertilization typically occurs in this specific location within the female reproductive system.

3. **Evaluating the Relationship:**
- While both the assertion and reason are true, the reason does not explain why the fusion of sperm and ovum is termed fertilization.
- The assertion defines what fertilization is, while the reason simply states where it occurs.

4. **Conclusion:**
- Since both the assertion and reason are true, but the reason does not provide the correct explanation for the assertion, we conclude that the correct answer is that both the assertion and reason are true, but the reason is not the correct explanation of the assertion.

**Final Answer:**
Both assertion and reason are true, but reason is not the correct explanation of assertion.

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