The correct option is A Spore formation
The dominant phase in the plant body of Dryopteris is sporophytic. The spores are formed within sporangia. The mature sporangium consists of a stalk and body or capsule. The capsule encloses 8 or 16 mother cells which divide meiotically and form 32 or 64 haploid spores. The spore germinates and gives rise to gametophyte (prothallus). The male and female reproductive organs are antheridia and archegonia respectively. The male and female gametes are formed by mitotic division. The fertilization occurs in the presence of water resulting in the formation of diploid zygote.
So, the correct answer is 'spore formation'.