The ovule is the structure within the ovary of a flower that contains the female reproductive cells. It consists of various parts, including the megasporangium, which is the structure that houses the megaspore mother cell.
The megasporangium is responsible for producing and protecting the megaspore mother cell. The megaspore mother cell then undergoes meiosis, resulting in the formation of megaspores.
Therefore, the correct answer is (B) Megasporangium.