The correct option is C Assertion is true but Reason is false
One hypodermal nucellar cell of the micropylar region differentiates into the sporogenous cell. It forms a diploid megaspore mother cell or megasporocyte. The megaspore mother cells undergo meiosis and formed a row of four haploid megaspores. Only the chalazal megaspore remains functional megaspore enlarges and gives rise to female gametophyte, also called embryo sac.