Sexual Reproduction In Flowering Plants

Megasporogenesis is the process by which the megaspore mother cell within the ovule gives rise to megaspores, explained in NCERT Class 12, Chapter 2 (Sexual Reproduction in Flowering Plants). The diploid megaspore mother cell undergoes meiosis to produce four haploid megaspores arranged usually in a linear tetrad. In most angiosperms only one of these four megaspores remains functional, while the other three degenerate. This single functional megaspore enlarges and divides mitotically to form the seven-celled, eight-nucleate embryo sac. The option two is incorrect because only one survives in the monosporic type of development typical of NCERT examples. Three is wrong since three megaspores are the ones that actually degenerate, not the survivors. Four is incorrect because, although meiosis yields four megaspores, three are lost. A numerical sanity check fits this: four megaspores produced minus three that degenerate leaves exactly one functional megaspore, which is the precise figure asked for in the question.