Answer:
The correct answer would be D. seeds.
Ferns refer to the vascular plants which usually reproduce via spores.
They neither have seeds nor they have flowers.
They also show alternate of generation in which diploid sporophyte is a dominant phase of the life.
The diploid sporophyte produces spores through meiosis.
The spores divide through mitotic divisions and get developed into haploid gametophytes.
The gametophyte produces haploid gametes which fertilize to produce a diploid zygote.
The zygote develops and grows into mature sporophyte through mitotic divisions.