Assertion : Some female animals permit copulation only during oestrous cycle.
Reason : Oestrous cycle is observed in non-primate mammals.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Explanation

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Some female animals permit copulation only during the oestrous cycle." This means that there are specific times when female animals are receptive to mating, which is during their oestrous cycle.

2. **Understanding the Reason**:
- The reason provided is that "Oestrous cycle is observed in non-primate mammals." This indicates that the oestrous cycle, which is a reproductive cycle, occurs in mammals that are not classified as primates.

3. **Analyzing the Assertion**:
- The assertion is indeed correct. In many non-primate mammals, such as cows, sheep, and dogs, females only allow mating during the oestrous phase when they are in heat.

4. **Analyzing the Reason**:
- The reason is also correct. The oestrous cycle is primarily observed in non-primate mammals, which distinguishes them from primates that have a menstrual cycle.

5. **Evaluating the Relationship**:
- Although both the assertion and reason are correct, the reason does not serve as a correct explanation for the assertion. The assertion is about the timing of copulation in relation to the oestrous cycle, while the reason merely states that this cycle is present in non-primate mammals without explaining why females permit copulation only during this cycle.

6. **Conclusion**:
- Therefore, the correct answer is that both the assertion and reason are correct, but the reason is not the correct explanation for the assertion. The answer choice that reflects this is option B.