Assertion: Megaspore mother cell undergoes meiosis to produce four megaspores.

Reason: Megaspore mother cells and megaspores both are haploid.

The correct option is B

An assertion is correct but the reason is incorrect.

The correct option is B:

Explanation for the Correct option:

Assertion:

1. The diploid megaspore mother cell develops inside the nucleus.
2. It then passes through the meiotic division to form four haploid megaspores.
3. Therefore, the assertion is true.

Reason:

1. The megaspore mother cell is diploid and the megaspore is haploid.
2. Thus, the reason is wrong.

Final answer: An assertion is correct but the reason is incorrect.