Why can't you go to a garden store and buy fern seeds?
(a) ferns do not produce seeds.
(b) fern seeds are too small to package.
(c) fern seeds are very rare.
(d) fern seeds must stay moist.

A, as in Apple

organisms that lack symmetry are called asymmetrical and belong to phylum porifera/sponges.

organisms with specialized stinging cells belong to phylum cnidaria. stinging cells are called cnidoblast cells.

cnidarians show two morphological forms : polyp (sessile) and medusa (mobile)

filter feeding is observed in porifera members.  

alternation of generation is observed in coelenterata or cnidaria. there is alternation of asexual polyp form and sexual medusoid form. it is also referred as metagenesis.