Organisms belonging to the domains Archaea and Eubacteria are composed of single
cells. What criterion is used to classify each type of organism into a separate domain?

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.

i believe it would cause an increase of percipitation, though i could be wrong. so i would say b is the answer.

several tissues working together form an organ, and several organs together make up an organisms.

the group of cell that carries out special jobs are tissue.