The correct option is B 150
In an ovule, generally one megaspore mother cell (MMC) undergoes meiosis to form four megaspores. One of the megaspore remains functional and leads to the formation of the embryo sac (female gametophyte) while, the other three are non-functional and degenerate.
If the number of ovules is 50, the number of megaspores formed is 50 x 4 = 200.
If 3/4 megaspores degenerate from each ovule, then, 200 x 3/4 = 150.
Therefore, the number of non-functional megaspores formed in the ovary is 150.