Ans.
Ferns are vascular plants, which reproduce through spores and do not have seeds and flowers. Life cycle of ferns shows two different phases, sporophyte and gametophyte.
The sporophyte represents diploid stage that releases spores through meiosis. The spores are released from sporangia, found under the fronds of sporophyte. These spores grow into heart-shaped, small plant, which represents haploid gametophyte stage.
The male and female organs, present in mature gametophyte undergo fertilization and form zygote. The zygote develop into mature sporophyte by mitosis, which again makes gametophyte.
Thus, the correct answer is option). 'spores.'
